*For a thicker, glaze-like dressing, use an aged or reduced balsamic.
Preheat grill to medium. Place all vinaigrette ingredients in a blender, blend until smooth and set aside. Slice watermelon into ½- to 1-inch rounds, place rounds on grill and cook about 5 min. per side, until tender with nice grill marks. Remove rounds from grill, sprinkle each with sea salt and cut into wedges (smaller for finger food servings, larger for individual plated servings). Place wedges onto serving plates or platter, top each wedge with feta and mint, then finish with a drizzle of vinaigrette.