Here are the wood pieces and their measurements for the bottom portion of the wood box:
TWO 4-3/4" X 5-1/2" X 3/4" pine wood
TWO 9-1/4" X 1-5/8" X 3/4" pine wood
You'll want to cut, sand smooth then assemble these four pieces as shown in the photo using your choice of glue, brad nailer or old fashion hammer and nails. We glued and then used the brad nailer.