I just used a Walmart polyester batting. I stitched around the outside with the backing and top on top of the batt leaving about a 12 inch opening for turning. I then trimmed away all the fabric and batting to the 1/4 inch seam allowance and clipped the corners a bit. I turned it inside out through the opening and smoothed it out flat. I gave it a light press with a warm iron (not hot as it can melt the polyester batt) and then put it right up on the frame. The clips went on and I just rotated them until the whole sandwich was taut.