Cut your watermelon in half lengthwise, then into cubes roughly the size of dice—about three-quarters of an inch. I always taste a piece first to make sure it's actually ripe and sweet. You want that snap when you bite through the flesh, not a mealy texture that signals picked-too-early fruit.
Crumble your feta cheese directly into a large mixing bowl. Use your fingers to break it into small, uneven pieces rather than trying to be precious about it. The irregularity actually catches the dressing better than uniform chunks would.
In a separate small bowl, whisk together lime juice, honey, and olive oil until the honey dissolves completely. This takes about 45 seconds of actual whisking—I learned this the hard way after serving a salad with undissolved honey granules that caught between Connor's teeth. The emulsion should look slightly thicker than just liquid.
Add sea salt and black pepper to your dressing and whisk once more. Taste it on your finger—it should punch your palate with brightness and salt, because the watermelon will mellow it considerably. This is my vulnerable moment: I've absolutely served this underseasoned before, so I always err toward adding more salt than feels right.
Add your cubed watermelon to the bowl with feta. Gently toss to combine, being careful not to crush the fruit into mush. I use two wooden spoons and fold rather than stir, which keeps the watermelon pieces intact. This is why this 4th of july watermelon salad family recipe looks so pretty on the table—the fruit stays whole and glistening.
Pour your dressing over everything and toss once more, very gently. Add the diced cucumber and toss again. Now add your fresh mint and fold it in with those same two wooden spoons.
Let the salad sit at room temperature for exactly 10 minutes—not longer, or the watermelon releases too much liquid and dilutes the dressing. I set a phone timer for this because I'm not good at keeping track otherwise. After exactly 10 minutes, top with those toasted pistachios.