Prep the Fruit: Cube half of a seedless watermelon into bite-sized pieces and place them into a large, potluck-friendly serving bowl.
Add Savory Elements: Evenly crumble 6 ounces of block feta cheese over the watermelon, then scatter the thinly sliced red onion across the top.
Garnish with Herbs: Sprinkle 1/4 cup of finely chopped fresh mint leaves over the mixture for that signature summer freshness.
Whisk the Dressing: In a separate small jar or bowl, vigorously shake or whisk together 3 tablespoons of olive oil, 1 tablespoon of fresh lime juice, and a pinch of black pepper.
Toss & Chill: Pour the dressing gently over the salad right before transporting, and toss lightly so the feta doesn't break down too much. Keep chilled in a cooler or fridge until the exact moment of serving.