Arrange the watermelon cubes in a single layer on a parchment-lined baking sheet. Place in the freezer and freeze until completely solid, at least 3-4 hours or preferably overnight. Do not skip this step — frozen watermelon is what creates the smooth, scoopable sorbet texture without a machine.

Once the watermelon is fully frozen, remove the baking sheet from the freezer. Let the cubes sit at room temperature for 3-4 minutes to take the hardest edge off the freeze, which helps your blender process them more smoothly.

Add the frozen watermelon cubes to a high-speed blender or food processor in batches. Add the fresh lime juice, lime zest (if using), honey or agave, and a pinch of fine sea salt.

Blend on high speed, stopping to scrape down the sides as needed, until the mixture is completely smooth and creamy with no chunks remaining. Use the tamper if your blender includes one. Taste and adjust sweetness with additional honey if desired.

For soft-serve style sorbet: serve immediately, scooped into bowls or cones. For firm, scoopable sorbet: transfer the blended mixture to a freezer-safe container with a lid. Press a piece of plastic wrap directly onto the surface of the sorbet, then place the lid on. Freeze for at least 2 hours until firm.

To serve after freezing firm, remove the container from the freezer and let it sit at room temperature for 8-10 minutes to soften slightly. Scoop into bowls or cones and garnish with fresh mint leaves and a thin slice of watermelon. Serve immediately.