Place the watermelon cubes into the blender jar, ensuring they fill no more than halfway.
Add fresh lemon juice, honey (if using), and chopped mint leaves to the blender.
Secure the lid on the blender and blend on high speed until the mixture is completely smooth and vibrant in color, about 30-45 seconds. You should see a uniform, translucent blend with no chunks.
Strain the blended mixture through a fine sieve or strainer into a large pitcher, pressing gently with a spatula or spoon to extract as much liquid as possible, leaving pulp and solids behind.
Add a pinch of coarse salt and stir well to enhance the flavors. Fill glasses with ice cubes and pour the chilled watermelon lemon mixture over the ice.
Garnish each glass with a sprig of fresh mint or a thin wedge of lemon for presentation. Serve immediately for a refreshing, icy drink.