In a skillet over medium heat, cook ground beef and onion until browned. Add minced garlic and cook for another minute. Drain excess fat.
Transfer the beef mixture to your Crockpot. Add crushed tomatoes, tomato sauce, beef broth, Italian seasoning, red pepper flakes, salt, and pepper. Stir well.
Cover and cook on Low for 6–7 hours or High for 3–4 hours.
About 30 minutes before serving, add broken lasagna noodles to the Crockpot and stir. Cook until noodles are tender.
In a small bowl, mix ricotta, mozzarella, and Parmesan cheese.
To serve, ladle soup into bowls and top each serving with a spoonful of the cheese mixture. Garnish with basil or parsley.