Have you seen cube-shaped watermelons? They are certainly easier to store and sell. You don’t need to be a genius genetic engineer to make a square watermelon though. This Square Watermelon Mold makes the job easy. It is made of Polycarbonate plastic and fully transparent. All its parts are designed for outdoor use. The size of the melon your mold will produce is 7.5″ at its tallest point and 7.5″ at its widest. You can grow watermelons up to 12 lbs. You may want to check the list of suggested watermelon seed types that will work before getting started.