1. Grease slow cooker.
2. In a large skillet over medium-high heat, cook beef, onion, and garlic until beef is no longer pink. Drain excess fat. Stir in tomatoes, tomato paste, oregano, basil, sugar, salt, and black pepper.
3. In a medium bowl, combine ricotta cheese, Parmesan cheese, eggs, and parsley.
4. Layer 1/3 of the lasagna noodles in the bottom of the slow cooker. Top with 1/2 of the beef mixture, 1/2 of the ricotta mixture, and 1/2 of the mozzarella cheese. Repeat layers. Top with remaining lasagna noodles and beef mixture. Cover and cook on low for 4-5 hours.
5. Sprinkle remaining mozzarella cheese over the top. Cover and cook for an additional 30 minutes, or until cheese is melted.
6. Serve hot.