Stand the side boards up on their edges and position the top board over them evenly. Push the side boards to the sides of the top board as far as they will go so that their outside edges are flush with the outside edges of the top board.
Predrill four evenly spaced holes down through the top board and into the center of each side board. Attach the top board to the two side boards with wood screws.
Turn the stool over on its side and position the front board on top of the stool so that its top edge is flush with the top edge of the top board, and its side edges are flush with the outside edges of the side board. Position it so that there are 4 1/2 inches of open space at the bottom of the stool, which will serve as an easy place to pick up the stool; this will also give the impression that the side boards are the legs of the stool.
Predrill three evenly spaced holes through the front board and into the center of each side board and the top board, for nine holes in all. Attach the front board to the stool with wood screws. Repeat the process to attach the rear board.