Cut house pieces from plywood using a circular saw. (Note: Based on the measurements of our pictured side table, you will need two rectangle pieces that measure 21 5/8 by 28 inches, plus two triangles that are 21 5/8 inches wide, 26 inches in height and 33.8 inches on each side.) On one of the triangles, cut a 10-inch circle in the center. (Note: This will serve as the "door" to your cat's litter box enclosure.) Use the saw to angle-cut the top and bottom at a 45-degree angle.