In a small bowl, whisk together all the ingredients for the dressing. Then spoon 1 tablespoon into each of 4 mason jars (12-16 ounce jars work best) with re-sealable lids.
Add 1 cup of watermelon, ½ cup cucumbers, 1 tablespoon feta cheese and 1 tablespoon basil to each jar. Place the lids on the jars and refrigerate until you’re ready to eat. Or toss in your cooler for on-to-go eating.
To serve, invert the jars several times to distribute the dressing. Or dump the contents out into a medium bowl, tossing gently to combine. Enjoy immediately.