1. In a skillet, cook ground beef, onion, and garlic over medium heat until meat is no longer pink. Drain.
2. Stir in marinara sauce, basil, oregano, salt, and pepper. Simmer for 5 minutes.
3. In a mixing bowl, combine ricotta, 1 cup mozzarella, and Parmesan cheese.
4. Spread a thin layer of meat sauce in the bottom of the slow cooker. Top with a layer of uncooked lasagna noodles (break to fit), a layer of cheese mixture, and a layer of meat sauce. Repeat layers until all ingredients are used.
5. Cover and cook on low for 4-5 hours or until noodles are tender.
6. Sprinkle with remaining mozzarella cheese. Cover and let stand for 10 minutes or until cheese is melted.