Use a chef's knife and cutting board to cut the ripe watermelon into approximately 1-inch cubes. Arrange the cubes on the cutting board, removing any seeds if present.
Measure 4 cups of the watermelon cubes and transfer them into the blender jar. Add 1 tablespoon of honey if desired for sweetness.
Secure the lid on the blender and blend on high speed for about 30 seconds, until the mixture is completely smooth and no chunks remain. Watch for a vibrant, uniform pink color and a frothy surface as visual cues of readiness.
Stop the blender and remove the lid carefully. Pour the blended watermelon smoothie into glasses, watching for a bright, slightly translucent appearance with a smooth texture.
Optionally, garnish with a small slice of watermelon or a sprig of mint. Serve immediately for the freshest flavor and optimal cooling effect.
