Cut the watermelon in half vertically so that you can cut 1-inch round slices of watermelon. Cut the slices evenly as you can so that you have flat pieces to cut circles from.
Using the 2.5-inch cookie cutter, cut out 12 round circles and place them on a platter.
Using the 2-inch cookie cutter, cut out 12 round circles and stack them in the middle of the 2.5-inch circles.
Wash and dry all of the fruits, flowers, and leaves. Decorate the watermelon cakes with them. If necessary, use tweezers to place the decorations. Refrigerate the cakes until ready to serve them. The cakes look and taste their best the day they are made.