Wash the watermelon
Cut the watermelon into slices, cubes, or balls
Remove the rind and seeds
Pat the pieces dry with paper towels
Place the pieces on a baking sheet in a single layer
Freeze the pieces until solid
Transfer the frozen pieces to a freezer-safe bag or container
Remove as much air as possible
Label the container with the date
Store in the freezer for up to 8 to 12 months