Nail together four 6’ 2x6s into a square. Use a framing square to make sure all the corners are 90 degrees. Use the pool as a guide for placing the interior joists; make those out of 2x6s as well. You want it to be tight enough for the lip of the pool to rest on, but not so tight that you won’t be able to easily remove it. Nail in two joists lengthwise, and two smaller perpendicular joists to frame in the pool.
After the decking is attached, screw on pre-painted trim boards to all four flush sides. Lift the main deck upright and mark the centers of each joist in the inside frame which will hold the pool. Drill holes at the center points just inside the joists. This will provide guides for the edge of your circle as well as a starting hole for your jigsaw blade, and will prevent you from cutting into the joists.
Lay the deck down flat, and draw two intersecting lines connecting the opposite drill holes to make an X. Drill a screw into the center point of the X. Make a compass by attaching a string to a pencil. Tie the string onto the screw, pull tight and draw the circular cut line with the pencil.
Place your primary deck on a level spot in your yard. Give the structure a tiered effect by resting the secondary decks on cinder blocks and cover the sides and space underneath with plywood. Get creative with how and where you arrange your secondary decks around the primary one.