Measure out 2 cups of cut up watermelon and add to blender.
Add 8 ice cubes to blender.
(Optional) Add lemon juice.
Blend for about 45 seconds, or until all ice cubes are fully broken down.
If not thick enough for your liking, add more ice cubes and blend again. Enjoy!
Notes
The number of ice cubes needed will vary depending on size of ice cubes. This is the ice cube tray I use. Lemon juice is optional and you can add more or less as you prefer.