Wash tomatoes and cut off stem ends and any blemishes. Cut them up roughly into large chunks or wedges equal to approximately half a standard plum tomato size, smaller if you have then energy, but my theory: why bother?
Peel as many cloves of garlic as you wish to use (I use a whole head of 8-10ish).
Cover the bottom of the pot with olive oil, set on low heat, and put whole cloves into oil and saute slowly, with the lid on, so they get soft and sweet, not smoking hot and crispy. Check and stir regularly.
When the garlic is soft, dump the cut tomatoes on top of it, filling the pot.
When the tomatoes start to simmer, roughly chop basil and toss it in, covering pot again. I probably use 1/4 cup chopped, but more or less is up to you. Set the timer to uncover and stir every half hour for perhaps two hours, until the tomatoes are very soft. Then use a hand potato masher to squash the tomatoes right in the pot.
Leave uncovered and let simmer, stirring more often, until desired thickness is reached, perhaps another hour and a half. Cooking times vary widely depending on how wet or dry the tomatoes were.
Chop parsley (again to taste) and incorporate just as you turn off the heat, so it wilts.
Ladle cooled sauce into containers and freeze them as is. If you prefer a smooth sauce, you can blend now, or when using.