Step 1: Getting Started
You'll also need 1 1/2" deck screws and either 2 inch deck screws or nails. You may want to get some small hinges, but we'll get into that later.
Step 2: Start cutting and gluing
Second: You'll need to cut 4 4 foot long pieces of your 2'x4'. I then took each one and glued it to the long side of the plywood. Make sure it's flush with the edge of the board. Clamps make this much easier. (you can skip the glue and go directly to the screwing of the board, but I had a bottle of glue around)
Third: Predrill the holes and make sure to countersink the heads of the screw. Then use your 1 1/2" deck screws to hold them in place.
Step 3: Now for the Short Sides
Then attach them the same way as you did the first pieces. The construction part is now over half done, stand back and bask in your creating abilities.