Use a chef's knife and cutting board to dice the watermelon into approximately 1-inch cubes, ensuring uniform size for even distribution.
Transfer the cubed watermelon into a large mixing bowl.
Crumble the feta cheese over the watermelon, spreading it evenly throughout the bowl.
Chop the fresh mint leaves finely and sprinkle them over the salad mixture.
Drizzle the olive oil and balsamic vinegar over the ingredients in the bowl, then gently toss to combine all components thoroughly, ensuring the dressing coats the fruit and cheese evenly.
Serve immediately in bowls or on plates, garnished with additional mint if desired.