Using long sharp knife, cut a thin slice from end of watermelon, being careful not to cut into flesh of watermelon. Stand watermelon on cut end. Using a washable marker, mark handle at top of basket by drawing 2 parallel lines that are 2 1/2 inches apart, starting at top of watermelon and drawing lines about 6 inches down each side.
Using a sharp knife, cut out a wedge-shaped piece of watermelon from each side, leaving the handle intact. Using a large spoon, gently scoop out watermelon flesh, leaving about 4 inches of flesh at bottom of watermelon.
With a small knife or garnishing tool, make “V” or scallop cuts about 2 inches apart on cut sides and handle of watermelon basket.
Cut watermelon into 1-inch chunks or use melon ball tool to make balls of watermelon. Measure 3 cups of watermelon and place in large bowl. Refrigerate remaining watermelon for another use.
Add grapes and cantaloupe to watermelon in bowl. Gently mix in 1/4 cup mint, the lemon juice and sugar. Refrigerate fruit mixture and watermelon basket separately until ready to use. Just before serving, fill watermelon basket with fruit mixture. Garnish with strawberries and additional mint leaves.