For the watermelon and salad: Cut the watermelon into 2-inch squares that are 1/3-inch thick. Sprinkle them lightly with salt on one side. Lay the squares on flat surfaces that can fit inside the zip-top bags. Seal, pressing out as much air as possible. Place something on top of the bags that will provide gentle, even pressure, such as a plate with a few 15-ounce cans or a few bags of frozen peas on top. Freeze for 2 hours.

When the watermelon is ready, it will look flatter and have a denser texture. Transfer to a serving bowl; add the frisee and toss gently.

For the dressing: Whisk together the vinegar, sugar, lemon zest and juice, and oil in a liquid measuring cup to form an emulsified dressing.

Pour half of the dressing over the watermelon and frisee; toss gently to coat. Scatter the mozzarella cubes and coconut on top.

Serve right away; pass the remaining dressing at the table.