Prepare the garlic as you prefer. If you only want the flavor of garlic without having to eat it, leave the garlic whole in the sauce and remove later. If you like garlic, chop it up to make it a full-fledged part of the sauce.
In a medium saucepan, cook the garlic in the olive oil for five minutes over medium-low heat. Add 2 to 3 basil leaves and stir for a minute. Add the tomatoes and the rest of the basil. Bring the sauce to a boil and season conservatively with salt and pepper. Turn the heat to low and let it simmer for 30 minutes. Taste again for salt and pepper.