Tomato and Watermelon Salad

3/4-inch-cubed yellow or red seedless watermelon flesh, yellow or red seedless

English or regular cucumber, peeled, seeded, and cut into 3/4-inch cubes, small

Hass avocado, halved, pitted, peeled, and cut into 3/4-inch cubes

Heirloom tomatoes, small to medium

Balsamic vinegar, aged

Black pepper, freshly ground

Coriander seed

Kosher salt and freshly ground black pepper

Olive oil, extra virgin