Position the plywood on the 14-inch edges, parallel and 27 inches apart. You may need an extra pair of hands to keep the plywood in this position and to make the next step easier.
Position a 27-inch board perpendicularly between the boards so it is 3 inches above the ground and flush with the two corresponding 24-inch edges of the plywood.
Screw through the plywood and into the ends of the board. Screw another 24-inch board to the plywood in the same manner. It should be 3 inches above the ground, and flush with the 24-inch edges on the opposite side. This pair of boards is the bottom shelf for your shoe rack.
Screw another pair of boards to the plywood so there is a board directly above each of the first two. This second pair of boards should be 8 inches above the first and flush with the 24-inch edges of the plywood just as the first are. Repeat this step so there is a third pair of boards 8 inches above the second pair.