Precut the sides of your nesting box from the half sheet of 1-inch plywood. Using a carpenter's pencil and a tape measure, measure off two 18-inch by 14-inch boards. Mark a diagonal line running between the 18-inch side and the 14-inch side for each of the two boards; cut each board out using a jigsaw.
Nail your nesting box mounting boards in place in your chicken coop. Position the first board approximately 20 inches from the floor of your coop and parallel to the floor. Nail the board in place against the wall of your chicken coop. Position the second board approximately 18 inches above and parallel to the first board. Nail this board into place on the wall of your chicken coop as well.
Attach the bottom and sides of your wood nesting box. Rest the nesting box bottom along the top edge of the lower mounting board, parallel to the lower mounting board. Nail this board firmly to the lower mounting board. Rest one nesting box side against the nesting box bottom, positioning it with the diagonal edge at the top. Make sure the top back edge of the nesting box side (the 18-inch side) rests against the top mounting board. Nail the nesting box side to the top mounting board and to the bottom of the nesting box. Repeat this procedure for the other side of the nesting box.
Attach the top of the nesting box. Lay the nesting box top gently across the top of your nesting box, making sure it rests on the top mounting board and overlaps the sides approximately 1 inch on each side. Nail the nesting box top to the top mounting board and to the sides of the nesting box.
Affix the nesting box lip in place. Rest the board horizontally across the bottom edge of your nesting box front opening and nail it in place. This board should decrease the height of your nesting box opening from 14 inches to 10 inches. According to BackYardChickens.com, this nesting box lip keeps your chickens from pushing nesting material and eggs out of the nesting box.