Lay two 48-inch boards on edge, parallel, and 17 inches apart. Screw through the ends of the 48-inch boards, into the ends of two 17-inch boards. The 17-inch boards should be perpendicular to the 48-inch boards, and the corners should be flush, creating a 20-inch-by-48-inch frame. Repeat this process with the other two 48-inch, and 17-inch boards.
Lay one frame flat, and position a 32-inch board vertically in each corner. Screw through 48-inch and 17-inch boards, into the 32-inch boards to secure the table legs. This is your table frame, but positioned upside down.
Lift the second 20-inch-by-48-inch frame, and screw it to the legs so it is parallel with the lower frame and 15-inch away. This will provide support for your lower shelf.
Turn your table frame upright. Screw your 20-inch-by-48-inch plywood to the top frame. Be sure all of the edges are flush. Screw the 20-inch-by-38-inch plywood to the bottom frame, ensuring all of the edges are flush.
Sand down your entire project with your medium grade sand paper, and then with your fine grade sand paper. Wipe your project down with a tack cloth, and apply your oil stain. Let your table dry according to instructions.