Heat a large skillet over medium heat. Add the ground beef, chopped onion, and minced garlic. Cook until the beef is browned and the onion is soft, then drain any excess fat.
Transfer the beef mixture to the slow cooker. Stir in the beef broth, crushed tomatoes, tomato paste, dried basil, and dried oregano. Season with salt and pepper.
Cover and cook on low for 6 hours.
Thirty minutes before serving, stir the broken lasagna noodles into the soup. Cover and continue cooking until the noodles are tender.
Ladle the soup into bowls. Add a spoonful of ricotta to each bowl and serve with garlic bread on the side.