Add the ground beef, onion, and 3 cloves of garlic to a skillet over medium heat, crumbling the meat as it cooks. Drain the grease from the skillet and add the marinara, tomato paste, Italian seasoning and 1 cup of water to the beef. Stir well to combine.
Spray a slow cooker with non-stick spray.
Place ¼ of the meat sauce into the bottom of the slow cooker.
Layer 1/3 of the noodles over the sauce, breaking them up to cover the entire area. The noodles will overlap a bit.
Add the ricotta, 1 cup of mozzarella, Parmesan, parsley, salt, and reserved 2 cloves of minced garlic to a small bowl and stir to combine.
Spoon ? of the ricotta mixture over the noodles. Repeat layers twice, ending with meat sauce.
Sprinkle with the reserved cup of mozzarella cheese.
Cover and cook on low for 5 hours or until noodles are tender.
The ricotta may be swapped for cottage cheese, if that's your preference.