Classic Ratatouille

Name: Classic Ratatouille
Ingredients: 2 to 3 small or medium eggplants (trimmed of the stem and diced into 1/2-inch cubes); 6 tablespoons olive oil (divided, plus more if needed); 3 medium onions (peeled, trimmed, and diced into 1/2-inch pieces); 8 to 10 cloves of garlic (peeled, and sliced thinly); 2 to 3 stems of fresh basil (tied together with kitchen twine, plus 6 to 8 additional fresh basil leaves for adding at the end); 1/4 teaspoon crushed red pepper flakes; 3 bell peppers (stemmed, seeded, and diced into 1/2-inch pieces); 2 medium yellow squash (trimmed of the stem and diced into 1/2-inch pieces); 2 zucchini (trimmed of the stem and diced into 1/2-inch pieces); 3 to 5 ripe tomatoes (cored, and diced into 1/2-inch pieces); 4 teaspoons salt (divided, or more to taste)