Set two 36-inch boards on edge, 34 inches apart, and set the 34-inch boards perpendicularly between them, so they're also on edge and 34 inches apart. Screw through the 36-inch boards and into the ends of the 34-inch boards. Use twelve screws for this task. You will have a 36-inch-by-36-inch frame.
Cut two 1-inch-wide-by-4-inch-deep notches in each of the remaining boards. The notches must be 2 inches away from each end of the boards, parallel with the ends and cut along the same edge of the board. Use your handsaw, hammer and chisel to cut out the notches.
Lay your frame flat where you would like to position your pyramid display stand for your plants. Set the 40-inch boards perpendicularly on top of the frame so the boards of the frame fit inside the notches. Space the 40-inch boards 26 inches apart.
Set the 30-inch boards perpendicularly on top of the 40-inch boards, so the 40-inch boards fit inside the notches of the 30-inch boards. Space the 30-inch boards 20 inches apart. Set the 24-inch boards perpendicularly on top of the 30-inch boards in the same manner, spaced 20 inches apart.
Set the 18-inch boards perpendicularly on top of the 24-inch boards in the same manner and space them 8 inches apart. Set the 12-inch boards perpendicularly on top of the 18-inch boards in the same manner and space them 8 inches apart. All of the the boards should be supported by the boards underneath fitting in to their notches.