This is probably the easiest, and dare I say tastiest, spaghetti sauce you'll have ever made. And the best part is, no mess to clean up! Try it, you'll love it!
Heat the oil in a 7qt Dutch oven set over medium heat. Add the onions, celery, bell pepper, garlic, salt and pepper and cook, stirring often, until softened and fragrant, about 3 minutes.
Add the ground beef and continue cooking, stirring and breaking the meat as you go, until the meat is brown and cooked through, about 10 minutes.
Add the diced and crushed tomatoes as well as all the herbs and spices and stir well. Bring to a simmer then kill the heat, cover and transfer the Dutch oven to the preheated oven.
Cook for 5 to 6 hours, stirring once or twice, until the sauce has reached the desired thickness and consistency.
Remove from oven, allow to rest for 15 to 20 minutes before serving over your favorite pasta.
Keep leftovers in the fridge for up to several days, or in the freezer for up to a few months.