Use a chef's knife and cutting board to carefully dice the watermelon into 1-inch cubes. Arrange the watermelon pieces in a large mixing bowl. Observe that the watermelon is evenly cut with vibrant red flesh and a juicy appearance.
Add crumbled feta cheese and sliced avocado to the bowl with the watermelon. Gently combine the ingredients using a spoon or spatula, ensuring the avocado maintains its shape and feta is evenly distributed. The mixture should look colorful and slightly glossy.
Chop fresh mint and basil leaves into small pieces and sprinkle over the salad. Mix well to distribute the herbs uniformly, adding visual brightness and aroma to the mixture.
In a small bowl or measuring cup, whisk together olive oil, lemon juice, salt, and pepper until the dressing is well combined and slightly emulsified. The dressing should have a light, glossy appearance.
Pour the dressing over the salad and gently toss until all ingredients are coated. The watermelon, feta, and avocado should glisten slightly, with herbs evenly dispersed, creating a fresh, colorful presentation.
Serve immediately in bowls, optionally garnished with additional herbs. The final dish should appear vibrant with a mix of reds, greens, whites, and a silky texture from the avocado.