In a small jar add all the marinade ingredients and shake well to emulsify.
Slice your watermelon into ½ - inch cubes and add it to a large bowl.
Pour your marinade over the watermelon, and gently toss to coat. Cover and refrigerate for up to 1 hour.
Meanwhile, prepare all the ingredients for your bowls.
Once the watermelon is ready, divide your cooked rice equally among 4 serving bowls along with your marinated watermelon as shown.
Top with carrot, fresh cucumber, edamame, radishes, and avocado as shown.
Drizzle with mayonnaise, garnish with green onions and sesame seeds.
Finish with a tiny drizzle of toasted sesame oil and red pepper flakes, if desired.