Cut the 3/4" plywood for the floor using a circular saw (Image 1). To get the curved corners, either use a template to draw the curves, or make a compass by hammering a nail into the center of the floor then attaching a string tied to pencil to the nail. Then hold the pencil upright and draw a curved line around each corner (Image 2).
After cutting with the jigsaw (Image 3), the subfloor should have a 14" radius, and the upper floor should measure a 13" radius. Use the same method to measure and cut the top of the house, matching the 13" radius of the upper floor. The drop, or leftover piece of wood from the top piece, should be saved for use later. Affix the upper floor onto the subfloor using wood glue and screws (Image 4).