Use a sharp knife to cut the watermelon into 1-inch cubes, removing the rind and any seeds as you go. You are looking for uniform pieces so every bite has a good ratio of watermelon to feta. Transfer the cubes to a large bowl.
3 Cups watermelon
Crumble the block feta over the watermelon with your fingers, aiming for pieces that are roughly the same size as a small pebble; not dust, not large chunks. You want feta in every bite without it dominating.
4 Tablespoons feta cheese
Drizzle it in a slow zigzag over the top of the salad. You want coverage without drowning it; a light, even coat is what you are after. If the glaze pools at the bottom, you used too much.
2 Tablespoons balsamic glaze
Chop the mint leaves finely and scatter them over the top. You should see flecks of green throughout; if it looks sparse, add a few more leaves.
Fresh Mint
Use a large spoon or salad tongs and fold the ingredients together with 3 or 4 slow turns. You are not trying to fully coat everything; you are just bringing the layers together. The watermelon cubes are fragile once cut and will break down if you toss aggressively.