1 medium or 2 small eggplant, cut into 1/2-inch dice
4 tablespoons olive oil, divided, plus more to taste
2 medium onions, cut into 1/2-inch dice
4 to 6 garlic cloves, chopped
1/2 bunch of basil, tied in a bouquet with kitchen twine + 6 basil leaves, chopped
pinch of dried chile flakes
2 sweet peppers, cut into 1/2-inch dice
3 medium summer squash, cut into 1/2-inch dice
3 ripe medium tomatoes, cut into 1/2-inch dice
Salt to taste