Use the chef's knife and cutting board to cut the watermelon into manageable chunks, looking for flesh that is bright red and moist; remove seeds if present.
4 cups watermelon chunks
Place the watermelon chunks into the blender, adding lime juice, honey or agave syrup, and a pinch of salt.
4 cups watermelon chunks
Blend on high until the mixture is smooth with small seed bits and pulp visibly dispersed throughout; about 30-45 seconds. Stop and scrape down the sides if needed.
Pour the blended mixture through a fine mesh strainer into a pitcher, using a spoon to press the pulp and extract liquid, leaving seed bits and pulp behind. Discard solids.
Pour the strained juice into glasses filled with ice, garnish with lime slices if desired, and add tequila if using. Serve immediately for a chilled, pulpy drink.
4 cups watermelon chunks