Slow Cooker Lasagna

This is comfort food for the soul.  It's absolutely delicious!  All the right flavors with the right texture, in one awesome combination.  Enjoy!
-1 lb extra lean ground beef
-1 medium onion, finely chopped
-3 garlic cloves, minced
-1 (28 oz) can crushed tomatoes
-1 (15 oz) can tomato sauce
-2 tsp salt
-2 tsp dried oregano
-1 tsp dried basil
-1 tsp crushed red pepper flakes
-1 cup ricotta cheese
-2 cups shredded mozzarella cheese, divided
-6 lasagna noodles
-1 cup shredded Parmesan cheese
Place beef, onion and garlic in large skillet.  Cook until beef is nicely browned (make sure to break the clumps while cooking).
Add the crushed tomatoes, tomato sauce, salt, oregano, basil and pepper flakes.  Give a good stir.  Let simmer for 5 minutes.
While that's simmering, mix the ricotta with 1 cup of the mozzarella.  Mix well.
Coat the bottom and sides of your slow cooker with cooking spray.
Spoon 1/3 of the beef mixture on the bottom of slow cooker.  Break 3 of the noodles in half and arrange on top of sauce.  Top noodles with half of the ricotta mixture.  Repeat layers: sauce, noodles, ricotta.  Top with remaining 1/3 of the sauce.
Cover and cook on low for 3-3:30 hours.
In a small bowl, combine remaining mozzarella with the Parmesan.
Once the lasagna is done cooking, turn off the slow cooker.  Uncover and sprinkle the Parmesan mixture on top.  Let it sit for 10-15 minutes so that the cheese on top can nicely melt and the lasagna to set.
Cut into serving sizes and enjoy!