Add the frozen watermelon, 1 tbsp maple syrup, lime juice, and mint or basil, to a high-speed blender.
Pulse the blender until the watermelon starts to break up some, then blend to form a thick, slushie consistency.
Adjust the maple syrup to taste, adding more if necessary.
If the mixture is too thick for your liking, you can add in a little water. If it is too thin, add more watermelon!
Serve cold and enjoy!