diff --git a/codex-plonky2-circuits/src/circuits/mod.rs b/codex-plonky2-circuits/src/circuits/mod.rs
index 744d84d..41bb46e 100644
--- a/codex-plonky2-circuits/src/circuits/mod.rs
+++ b/codex-plonky2-circuits/src/circuits/mod.rs
@@ -1,4 +1,6 @@
 pub mod capped_tree_circuit;
 pub mod safe_tree_circuit;
 pub mod prove_single_cell;
-pub mod sample_cells;
\ No newline at end of file
+pub mod sample_cells;
+pub mod utils;
+pub mod params;
\ No newline at end of file
diff --git a/codex-plonky2-circuits/src/circuits/params.rs b/codex-plonky2-circuits/src/circuits/params.rs
new file mode 100644
index 0000000..1bfb1c4
--- /dev/null
+++ b/codex-plonky2-circuits/src/circuits/params.rs
@@ -0,0 +1,20 @@
+// global params for the circuits
+// only change params here
+
+use plonky2::hash::poseidon::PoseidonHash;
+
+// constants and types used throughout the circuit
+pub const N_FIELD_ELEMS_PER_CELL: usize = 4;
+pub const BOT_DEPTH: usize = 5; // block depth - depth of the block merkle tree
+pub const MAX_DEPTH: usize = 16; // depth of big tree (slot tree depth + block tree depth)
+pub const N_CELLS_IN_BLOCKS: usize = 1<<BOT_DEPTH; //2^BOT_DEPTH
+pub const N_BLOCKS: usize = 1<<(MAX_DEPTH - BOT_DEPTH); // 2^(MAX_DEPTH - BOT_DEPTH)
+pub const N_CELLS: usize = N_CELLS_IN_BLOCKS * N_BLOCKS;
+
+pub const DATASET_DEPTH: usize = 2;
+pub const N_SAMPLES: usize = 5;
+
+// hash function used. this is hackish way of doing it because
+// H::Hash is not consistent with HashOut<F> and causing a lot of headache
+// will look into this later.
+pub type HF = PoseidonHash;
\ No newline at end of file
diff --git a/codex-plonky2-circuits/src/circuits/prove_single_cell.rs b/codex-plonky2-circuits/src/circuits/prove_single_cell.rs
index cdc53b9..13ef578 100644
--- a/codex-plonky2-circuits/src/circuits/prove_single_cell.rs
+++ b/codex-plonky2-circuits/src/circuits/prove_single_cell.rs
@@ -29,18 +29,8 @@ use plonky2::plonk::config::PoseidonGoldilocksConfig;
 
 use plonky2::hash::hashing::PlonkyPermutation;
 use crate::circuits::safe_tree_circuit::{MerkleTreeCircuit, MerkleTreeTargets};
-
-// constants and types used throughout the circuit
-pub const N_FIELD_ELEMS_PER_CELL: usize = 4;
-pub const BOT_DEPTH: usize = 5; // block depth - depth of the block merkle tree
-pub const MAX_DEPTH: usize = 16; // depth of big tree (slot tree depth + block tree depth)
-const N_CELLS_IN_BLOCKS: usize = 1<<BOT_DEPTH; //2^BOT_DEPTH
-const N_BLOCKS: usize = 1<<(MAX_DEPTH - BOT_DEPTH); // 2^(MAX_DEPTH - BOT_DEPTH)
-const N_CELLS: usize = N_CELLS_IN_BLOCKS * N_BLOCKS;
-// hash function used. this is hackish way of doing it because
-// H::Hash is not consistent with HashOut<F> and causing a lot of headache
-// will look into this later.
-type HF = PoseidonHash;
+use crate::circuits::utils::usize_to_bits_le_padded;
+use crate::circuits::params::{MAX_DEPTH, BOT_DEPTH, N_FIELD_ELEMS_PER_CELL, N_CELLS_IN_BLOCKS, N_BLOCKS, N_CELLS, HF};
 
 // ------ Slot Tree --------
 
@@ -157,9 +147,9 @@ impl<F: RichField, H: Hasher<F>> SlotTree<F, H> {
 
     /// verify the given proof for slot tree, checks equality with given root
     pub fn verify_cell_proof(&self, proof: MerkleProof<F, H>, root: HashOut<F>) -> Result<bool>{
-        let mut block_path_bits = self.usize_to_bits_le_padded(proof.index, MAX_DEPTH);
+        let mut block_path_bits = usize_to_bits_le_padded(proof.index, MAX_DEPTH);
         let last_index = N_CELLS - 1;
-        let mut block_last_bits = self.usize_to_bits_le_padded(last_index, MAX_DEPTH);
+        let mut block_last_bits = usize_to_bits_le_padded(last_index, MAX_DEPTH);
 
         let split_point = BOT_DEPTH;
 
@@ -186,18 +176,18 @@ impl<F: RichField, H: Hasher<F>> SlotTree<F, H> {
         return block_tree;
     }
 
-    /// Converts an index to a vector of bits (LSB first) with padding.
-    pub(crate) fn usize_to_bits_le_padded(&self, index: usize, bit_length: usize) -> Vec<bool> {
-        let mut bits = Vec::with_capacity(bit_length);
-        for i in 0..bit_length {
-            bits.push(((index >> i) & 1) == 1);
-        }
-        // If index requires fewer bits, pad with `false`
-        while bits.len() < bit_length {
-            bits.push(false);
-        }
-        bits
-    }
+    // /// Converts an index to a vector of bits (LSB first) with padding.
+    // pub(crate) fn usize_to_bits_le_padded(&self, index: usize, bit_length: usize) -> Vec<bool> {
+    //     let mut bits = Vec::with_capacity(bit_length);
+    //     for i in 0..bit_length {
+    //         bits.push(((index >> i) & 1) == 1);
+    //     }
+    //     // If index requires fewer bits, pad with `false`
+    //     while bits.len() < bit_length {
+    //         bits.push(false);
+    //     }
+    //     bits
+    // }
 }
 
 //------- single cell struct ------
@@ -329,14 +319,14 @@ impl<
         }
 
         // Convert `leaf_index` to binary bits and assign as path_bits
-        let path_bits = self.usize_to_bits_le_padded(leaf_index, MAX_DEPTH);
+        let path_bits = usize_to_bits_le_padded(leaf_index, MAX_DEPTH);
         for (i, bit) in path_bits.iter().enumerate() {
             pw.set_bool_target(targets.path_bits[i], *bit);
         }
 
         // get `last_index` (nleaves - 1) in binary bits and assign
         let last_index = N_CELLS - 1;
-        let last_bits = self.usize_to_bits_le_padded(last_index, MAX_DEPTH);
+        let last_bits = usize_to_bits_le_padded(last_index, MAX_DEPTH);
         for (i, bit) in last_bits.iter().enumerate() {
             pw.set_bool_target(targets.last_bits[i], *bit);
         }
diff --git a/codex-plonky2-circuits/src/circuits/safe_tree_circuit.rs b/codex-plonky2-circuits/src/circuits/safe_tree_circuit.rs
index 04c8f75..96e4bbf 100644
--- a/codex-plonky2-circuits/src/circuits/safe_tree_circuit.rs
+++ b/codex-plonky2-circuits/src/circuits/safe_tree_circuit.rs
@@ -18,6 +18,7 @@ use plonky2::plonk::proof::{Proof, ProofWithPublicInputs};
 use std::marker::PhantomData;
 use plonky2_poseidon2::poseidon2_hash::poseidon2::Poseidon2;
 use serde::Serialize;
+use crate::circuits::utils::usize_to_bits_le_padded;
 
 use crate::merkle_tree::merkle_safe::{MerkleTree, MerkleProofTarget};
 use crate::merkle_tree::merkle_safe::{KEY_NONE,KEY_BOTTOM_LAYER};
@@ -144,14 +145,14 @@ impl<
         pw.set_hash_target(targets.leaf, leaf_hash);
 
         // Convert `leaf_index` to binary bits and assign as path_bits
-        let path_bits = self.usize_to_bits_le_padded(leaf_index, depth);
+        let path_bits = usize_to_bits_le_padded(leaf_index, depth);
         for (i, bit) in path_bits.iter().enumerate() {
             pw.set_bool_target(targets.path_bits[i], *bit);
         }
 
         // get `last_index` (nleaves - 1) in binary bits and assign
         let last_index = nleaves - 1;
-        let last_bits = self.usize_to_bits_le_padded(last_index, depth);
+        let last_bits = usize_to_bits_le_padded(last_index, depth);
         for (i, bit) in last_bits.iter().enumerate() {
             pw.set_bool_target(targets.last_bits[i], *bit);
         }
@@ -234,25 +235,25 @@ impl<
 }
 
 // --------- helper functions ---------
-impl<
-    F: RichField + Extendable<D> + Poseidon2,
-    C: GenericConfig<D, F = F>,
-    const D: usize,
-    H: Hasher<F> + AlgebraicHasher<F>,
-> MerkleTreeCircuit<F, C, D, H> {
-    /// Converts an index to a vector of bits (LSB first) with padding.
-    pub(crate) fn usize_to_bits_le_padded(&self, index: usize, bit_length: usize) -> Vec<bool> {
-        let mut bits = Vec::with_capacity(bit_length);
-        for i in 0..bit_length {
-            bits.push(((index >> i) & 1) == 1);
-        }
-        // If index requires fewer bits, pad with `false`
-        while bits.len() < bit_length {
-            bits.push(false);
-        }
-        bits
-    }
-}
+// impl<
+//     F: RichField + Extendable<D> + Poseidon2,
+//     C: GenericConfig<D, F = F>,
+//     const D: usize,
+//     H: Hasher<F> + AlgebraicHasher<F>,
+// > MerkleTreeCircuit<F, C, D, H> {
+//     /// Converts an index to a vector of bits (LSB first) with padding.
+//     pub(crate) fn usize_to_bits_le_padded(&self, index: usize, bit_length: usize) -> Vec<bool> {
+//         let mut bits = Vec::with_capacity(bit_length);
+//         for i in 0..bit_length {
+//             bits.push(((index >> i) & 1) == 1);
+//         }
+//         // If index requires fewer bits, pad with `false`
+//         while bits.len() < bit_length {
+//             bits.push(false);
+//         }
+//         bits
+//     }
+// }
 
 
 // NOTE: for now these tests don't check the reconstructed root is equal to expected_root
diff --git a/codex-plonky2-circuits/src/circuits/sample_cells.rs b/codex-plonky2-circuits/src/circuits/sample_cells.rs
index 4b28b45..b6d0dd3 100644
--- a/codex-plonky2-circuits/src/circuits/sample_cells.rs
+++ b/codex-plonky2-circuits/src/circuits/sample_cells.rs
@@ -27,15 +27,11 @@ use plonky2::field::goldilocks_field::GoldilocksField;
 use plonky2::plonk::config::PoseidonGoldilocksConfig;
 
 use plonky2::hash::hashing::PlonkyPermutation;
-use crate::circuits::prove_single_cell::{MAX_DEPTH, SlotTree};
+use crate::circuits::prove_single_cell::{SingleCellTargets, SlotTree};
+use crate::circuits::params::{MAX_DEPTH, BOT_DEPTH, N_FIELD_ELEMS_PER_CELL, N_CELLS_IN_BLOCKS, N_BLOCKS, N_CELLS, HF, DATASET_DEPTH, N_SAMPLES};
+
 use crate::circuits::safe_tree_circuit::{MerkleTreeCircuit, MerkleTreeTargets};
 
-// constatnts and types
-const DATASET_DEPTH: usize = 2;
-const N_SAMPLES: usize = 5;
-
-type HF = PoseidonHash;
-
 // ------ Dataset Tree --------
 ///dataset tree containing all slot trees
 #[derive(Clone)]
@@ -155,6 +151,78 @@ impl<F: RichField, H: Hasher<F>> DatasetTree<F, H> {
     }
 }
 
+//------- single cell struct ------
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct DatasetTargets<
+    F: RichField + Extendable<D> + Poseidon2,
+    C: GenericConfig<D, F = F>,
+    const D: usize,
+    H: Hasher<F> + AlgebraicHasher<F>,
+> {
+    // pub expected_dataset_root_target: HashOutTarget,
+    // pub slot_index: Target,
+    // pub entropy_target: Target,
+    // pub slot_root: HashOutTarget,
+    pub slot_proofs: Vec<SingleCellTargets<F, C, D, H>>,
+
+
+    // pub proof_target: MerkleProofTarget,
+    // pub leaf_target: Vec<Target>,
+    // pub path_bits: Vec<BoolTarget>,
+    // pub last_bits: Vec<BoolTarget>,
+    _phantom: PhantomData<(C,H)>,
+}
+
+//------- circuit impl --------
+impl<
+    F: RichField + Extendable<D> + Poseidon2,
+    C: GenericConfig<D, F=F>,
+    const D: usize,
+    H: Hasher<F> + AlgebraicHasher<F> + Hasher<F>,
+> MerkleTreeCircuit<F, C, D, H> {
+
+    // the in-circuit sampling of a slot in a dataset
+    pub fn sample_slot_circuit(
+        &mut self,
+        builder: &mut CircuitBuilder::<F, D>,
+    )-> DatasetTargets<F,C,D,H>{
+
+        // Create virtual targets
+        // let slot_root = builder.add_virtual_hash();
+        let mut slot_proofs =vec![];
+        for i in 0..N_SAMPLES{
+            let proof_i = self.prove_single_cell2(builder);
+            slot_proofs.push(proof_i);
+        }
+
+        DatasetTargets::<F,C,D,H>{
+            // expected_dataset_root_target: HashOutTarget {},
+            // slot_index: Default::default(),
+            // entropy_target: Default::default(),
+            // slot_root: HashOutTarget {},
+            slot_proofs,
+            _phantom: Default::default(),
+        }
+    }
+
+    // assign the witnesses to the target
+    // takes the dataset tree, slot index, and entropy
+    pub fn sample_slot_assign_witness(
+        &mut self,
+        pw: &mut PartialWitness<F>,
+        targets: DatasetTargets<F,C,D,H>,
+        dataset_tree: DatasetTree<F,H>,
+        slot_index:usize,
+        entropy:usize,
+    ){
+
+
+    }
+
+}
+
+
 // --------- helper functions --------------
 fn calculate_cell_index_bits<F: RichField>(p0: usize, p1: HashOut<F>, p2: usize) -> Vec<bool> {
     let p0_field = F::from_canonical_u64(p0 as u64);
diff --git a/codex-plonky2-circuits/src/circuits/utils.rs b/codex-plonky2-circuits/src/circuits/utils.rs
new file mode 100644
index 0000000..77f62e6
--- /dev/null
+++ b/codex-plonky2-circuits/src/circuits/utils.rs
@@ -0,0 +1,17 @@
+
+
+
+// --------- helper functions ---------
+
+/// Converts an index to a vector of bits (LSB first) with padding.
+pub(crate) fn usize_to_bits_le_padded(index: usize, bit_length: usize) -> Vec<bool> {
+    let mut bits = Vec::with_capacity(bit_length);
+    for i in 0..bit_length {
+        bits.push(((index >> i) & 1) == 1);
+    }
+    // If index requires fewer bits, pad with `false`
+    while bits.len() < bit_length {
+        bits.push(false);
+    }
+    bits
+}
\ No newline at end of file