Place the cubed watermelon flesh into a blender.
Blend on high speed until the mixture is completely smooth and uniform, with no chunks remaining. You should see a bright pink liquid with a slightly frothy surface.
Pour the blended watermelon into a shallow, freezer-safe container and smooth the surface with a spatula.
Cover the container with a lid or plastic wrap and place it in the freezer. Every 30 minutes, remove and stir vigorously with a fork to break up ice crystals, repeating 3-4 times until the sorbet is evenly frozen and scoopable, about 2 hours total.
Once fully frozen and firm, scoop the sorbet into bowls. Serve immediately for a smooth, icy dessert.
