We all cut watermelon in the same way, so the pieces often crack or fall on the ground.
So, why do not you try doing it in a completely different way?
Cut the watermelon in half, carefully remove the rind and cut the halves into cubes. Cover it with a deep bowl or a container, whatever you may prefer, then turn it upside down. Be careful when turning the bowl, because the watermelon is quite juicy.
Serve and enjoy this refreshing delicacy!