Brown the ground beef in a skillet over medium heat and drain excess fat.
Add the diced onion and minced garlic to the skillet and sauté until softened.
Transfer the beef, onion, and garlic mixture to the slow cooker.
Stir in the crushed tomatoes, beef broth, and Italian seasoning.
Break the lasagna noodles into smaller pieces and add them to the slow cooker.
Cover and cook on low for 6-8 hours or high for 3-4 hours until noodles are tender.
Once the noodles are tender, stir in the ricotta, mozzarella, and Parmesan cheeses.
Stir until the cheeses are melted and fully incorporated, then season with salt and pepper to taste.
Serve hot, garnished with extra Parmesan or fresh herbs if desired.