Bring a medium pot of water to boil. Meanwhile, cut an "X" across the top of each tomato. Prepare an ice bath in a bowl and set it next to the stove.
Working in batches, submerge each tomato in the boiling water for 30 to 45 seconds, until the skin around the cut starts to pull back from the flesh. Immediately transfer the tomatoes to the ice bath and allow to cool for a moment. Remove the skins from the tomatoes and discard (or save for later use). Roughly chop the tomatoes, removing the cores and any tough pieces that remain, and discard.
In a large Dutch oven or heavy-bottomed pot over medium heat, add the olive oil, garlic and chile flakes. Cook for 1 to 2 minutes, allowing the garlic to become fragrant but careful not to burn the chile flakes.
Add the chopped tomatoes, salt and basil to the pot, stirring to combine. Allow the sauce to simmer, stirring often to prevent burning.
After 1 hour, remove and discard the basil. Continue cooking the sauce over medium heat.
When the sauce reaches your desired thickness, season with salt and sugar to taste.
Serve immediately, or allow to cool and transfer to quart containers and freeze for up to 6 months.