In a large, straight-sided skillet over medium heat, warm the oil. Add garlic and cook until just slightly golden. Add chile flakes if desired and cook 30 seconds.
Stir in tomatoes and juices, basil, salt and pepper.
Bring sauce to a simmer and cook until sauce is thick and tomatoes have mostly fallen apart, about 30 to 40 minutes. Adjust heat as needed to keep at a steady simmer. If using whole plum tomatoes, mash them up with the back of a spoon to help them break down. Remove sauce from heat and discard basil.