Preheat broiler. In 12-inch skillet heat 2 tablespoon of the oil over medium-high heat. Add squash, onion, sweet peppers, carrot, broccoli, and garlic. Cook and stir for 3 minutes. Add tomatoes, olives, and olive liquid. Cook, uncovered, for 2 minutes more or until tender.
Place flatbreads on large baking sheets. Lightly brush both sides with some of the remaining olive oil. Broil half at a time, 4 inches from the heat, 1 to 2 minutes on each side or until lightly browned and toasted.
Using slotted spoon, remove vegetable mixture from skillet and spoon on toasted flatbreads. Top with cheese. Sprinkle with 1/8 teaspoon black pepper. Broil 4 inches from heat for 2 minutes or until cheese softens. Drizzle with remaining olive oil. Sprinkle with sea salt and freshly ground pepper. Makes 4 servings.