Cut the watermelon in half with a large knife on a cutting board, then slice into 1-inch thick slices and remove the rind.
Cut the watermelon flesh into evenly sized 1-inch cubes, ensuring uniformity for even freezing and melting.
Arrange the watermelon cubes in a single layer on a baking sheet lined with parchment paper, ensuring they do not overlap.
Place the baking sheet with the watermelon cubes into the freezer and freeze for about 1 hour until solid and icy in texture.
Once frozen, transfer the watermelon cubes into an airtight container or wrap them tightly with plastic wrap, then store in the freezer for at least 4 hours or until fully frozen and firm.
Serve the frozen watermelon cubes directly from the freezer as a refreshing, icy snack that bursts with sweet juice when bitten into.