1/2 fresh watermelon, seeded and diced
1/4 teaspoon fine-grain sea salt
Juice of 2 large limes
1 1/2 cups elderflower liqueur, such as St. Germain
1/2 cup best quality vodka
Ice, for serving
To make watermelon ice cubes for serving, pour extra watermelon juice into ice cube trays and freeze overnight.