Measure and cut nine (9) 2" x 6" x 49 ½" and two (2) 2" x 4" x 49 ½" boards.

Lay the nine (9) 2" x 6" boards in a square pattern with the smooth side down on a smooth flat, clean area. Use a drop cloth, if necessary.

Lay the two (2) 2" x 4" boards across the nine (9) 2" x 6" boards with the insides of the 2" x 4"s 17-1/2" apart. Make sure the board layout is square at 49 ½" x 49 ½". Evenly space the 2" x 6"s under the 2" x 4"s when the layout is square. Screw each of the 2" x 6"s to the 2" x 4"s with 2 ½" screws. Evenly space two (2) screws per board.

Flip over the top assembly so that the 2" x 4"s are on the bottom. Rest the assembly on a few 2" x 6s" or 2" x 4"s so that it's raised an inch or so. Measure from both edges to find the exact center square. As the full top assembly is 49 ½" square, the center should be 24 ¾" from each edge. Mark the exact center with a pencil and start a screw in about ¼" inch in dead center. Tie a length of string to the screw and stretch it to the edge of the square. Tie the end to a pen or pencil that you hold straight up. Keep the string taut and trace around to make a perfect circle. The pencil or pen mark should touch the edges at each side so you can check for roundness.

Cut out the circle you marked with a jigsaw. Make sure not to cut through a screw previously attached to the 2" x 4"s. Moving a screw location may be necessary.