Place the watermelon cubes into a large mixing bowl. Use a sharp knife and cutting board to carefully cut the watermelon into uniform, bite-sized pieces, ensuring each piece is juicy and well-shaped.
Crumb the feta cheese over the watermelon in the bowl, distributing it evenly. Roughly chop the fresh mint leaves and sprinkle them over the mixture. Drizzle the olive oil and lime juice over everything.
Toss gently with a large spoon until the ingredients are well combined, ensuring the feta and mint are evenly distributed and coated with the dressing. Observe the mixture for a light sheen and vibrant colors.
Transfer the salad onto a serving plate or keep in the bowl. Optionally, garnish with additional mint leaves for presentation. Serve immediately while cold and the watermelon is juicy.