Hammer the nail into the top of the stake and hammer the wooden stake in the ground in the center of the area where you want the pool.
Measure the string to a length that is half the radius of your pool plus 12 inches, and tie one end to the nail.
Pull the string taut and rotate around the stake while making marks on the ground with the paint to outline the shape of your pool.
Start at the lowest spot in the pool area and remove the grass from that spot.
Remove all dirt and grass from the rest of the pool area with your shovel.
Lay the board edge side up out from the center stake. Place your level on the top edge to determine the levelness of the area. Carefully remove dirt from any high spots as you move the board around the pool area.
Remove any dirt clods or rocks that are left of top of the area.