Step 5: Cutting the tops and bottom
Now take a piece of the 1/4" panel and cut it 9" wide. Do this twice so that you have two strips of panel that are 9" wide by 24" long. This will leave you with one strip that is roughly 6 inches wide, hang on to this piece of scrap for later.
Take the two 9" wide sections and cut a piece that is 11 1/2" long out of each of them. The 11 1/2" piece is the bottom of your box and the 12 1/2" piece is the top.