Step 4: Layer the plywood with high-density three-inch upholstery foam (cut to the exact measurements of the plywood), medium-loft batting (cut a foot wider on each side), and your stitched-together rugs.
Step 5: Center the rows of stitching and pull the batting and rug taut against the underside of the plywood. Staple the rug to the underside of the plywood every two inches along one long side. While pulling at the rug, staple the opposite side of the bench in the same manner. The rug should be very taut, not at all baggy.