Put cherry tomatoes in a large bowl and season with salt and pepper. Add olives and toss. Whisk together olive oil, balsamic and red pepper flakes. Pour mixture over tomatoes and olives. Toss well to coat and let sit for at least 10 minutes and up to an hour. When ready to eat, arrange mozzarella in the center of a large platter (or arrange it on individual plates). Spoon tomato and olive mixture over mozzarella. Garnish with basil leaves.