On the surface of your wood, draw out a rectangle that measures 6 feet by 3 feet. Use an existing corner and edges. This is the desk top. Cut out your rectangle with the saw. You will have an "L" shaped piece of wood left over
Measure and draw out four rectangles that are 29 inches long by 6 inches wide on the short side of the "L." You will be able to draw out four rectangles next to each other. Cut out these rectangles.
Draw four more rectangles that are 29 inches by 6 inches on the long part of the "L" that is left over. These rectangles will be drawn in pairs on top of each other on the wood. Cut these rectangles out with the hand saw.
Make four "legs" out of the 29-inch by 6-inch pieces of plywood by pairing them up and screwing them together with the wood screws. You should have four pieces that are 29 inches long by 2 inches wide by 6 inches deep.
Attach the legs to the desk top at the corners. Screw down from the top of your desk through the wood and into the legs. Use a carpenter's square to make sure all legs are at a 90-degree angle to the desk top.