How to build the base of your DIY swamp cooler?
Start by taking the 23" 2x4 and 2 16" 2x4s and screw them together with 3" screws to make a a "c" shape. Use 2 screws for each joint. Place the 16" by 26" piece of plywood on top of the "C" shape you just made. Secure it with 3 evenly spaced 1 5/8 inch screws on each of the short sides, and 4 screws on the long side.