Place a large, sharp knife on a clean cutting board, and slice the watermelon directly over a big mixing bowl. This allows the sweet juice to drip into the bowl, keeping the fruit moist and flavorful.
Once sliced, gently transfer the watermelon slices to the bowl if needed, making sure to keep the juice pooled at the bottom.
Crumble the feta cheese right on top of the watermelon, resisting the urge to mash it — you want those salty, crumbly bites intact.
Chop the fresh mint finely and sprinkle it over the salad, releasing its bright aroma and cooling flavor.
Squeeze the juice of a fresh lemon over everything, then drizzle with olive oil to add a silky texture and depth of flavor.
Sprinkle freshly ground black pepper over the top to add a subtle spice kick, and gently toss everything together to combine the flavors without breaking the watermelon chunks.
Serve immediately, allowing the flavors to meld just before eating, for a crisp, salty-sweet burst with each bite.
