Open cans of tomatoes and, using an immersion blender, purée until smooth.
Finely chop garlic, or pulse it in a mini-food processor until quite small.
Heat a large, heavy bottomed pot over medium heat and add olive oil. When olive oil is hot, add garlic and stir continuously for a minute or two, taking care not to let the garlic brown.
Add about a 1/2 a cup of tomato purée to the pot and stir it into the garlic mixture. Let it cook for a minute and the olive oil will take on a golden colour. This will give the sauce a boost of flavour as the tomato sauce caramelizes in the garlic oil.
Add remaining tomato purée and salt. Stir well. Simmer on medium low heat for at least 4 hours. Sauce will thicken. Continue cooking if you want a thicker sauce.
Taste and adjust salt, if desired. Remember that you will be adding salt to most recipes that you will be using this base tomato sauce for.
Remove from heat. Cool completely, then portion into Zip-lock bags or containers and freeze.