Preheat oven to 300 degrees. Place basil and mint in the bottom of a large casserole. Place tomatoes on top of herbs, cut side up. Wedge the whole garlic cloves between the tomatoes. Top the tomatoes with the olive oil, salt and chili flakes. Bake uncovered for 1 1/2 hours, basting every half hour with pan juices. Bake until tomatoes are tender and slightly browned.