Wash all the fresh tomatoes. Cut a small "X" on the bottom of each tomato. Bring 8 quarts of water to a rapid boil. Drop-in tomatoes to boiling water. Boil for one minute or until you can see the peel beginning to separate from the vegetable. Remove each tomato with a slotted spoon. Dip each tomato in an ice, cold water bath. Allow the tomatoes to sit in the ice bath for one minute to stop the cooking process. Drain.
Once cool enough to handle, peel the remaining skin off the tomatoes. Cut tomatoes in half, removing the tough core. Gently squeeze to remove large seeds, but the removal of ALL seeds is not necessary. Coarsely chop tomatoes.
Place tomatoes in your slow cooker.
Mix the onions, garlic, tomato paste, vinegar, sugar, Italian seasoning, salt, and pepper till thoroughly combined.
Place dry ingredients in slow-cooker with tomatoes. Cover and cook, on HIGH for 4-5 hours or until tomatoes have broken down and are very soft.
Remove lid and ceramic slow cooker bowl. Allow to cool for 20 minutes, stir in fresh basil and thyme.
Process mixture with an immersion blender until smooth or process the sauce, in batches, in your food processor or blender.
Season with salt and pepper. It is ready to pour over your favorite pasta.