To create the base tier of the cake, cut 3 slices of watermelon, 1 to 2 inches thick, crossways through the center of the melon. Trim the rind from the watermelon slices, and place the largest slice onto a cake plate. Alternate layering sliced strawberries, slices of cantaloupe, and slices of fresh pineapple; follow with the second-largest watermelon slice. Repeat once more to make a layered fruit stack that looks like a cake.

Thinly slice a few pieces of the remaining melon and pineapple. With cookie cutters or a sharp knife, cut remaining fruit slices into decorative shapes. Decorate the cake tiers with the cut fruit shapes and remaining berries.