1. Prepare the Crust:

1. In a skillet over medium heat, brown the ground beef until fully cooked. Drain excess fat and stir in the marinara sauce, Italian seasoning, salt, and pepper.
2. In a bowl, mix the ricotta cheese, half of the mozzarella cheese, Parmesan cheese, and egg until well combined.
3. Spread a thin layer of the meat sauce on the bottom of a 6-quart slow cooker. Arrange 3 lasagna noodles over the sauce, breaking them to fit if needed.
4. Spread half of the ricotta mixture over the noodles, then top with a third of the remaining meat sauce. Repeat layers: noodles, remaining ricotta mixture, another third of the meat sauce, and the last 3 noodles.
5. Finish with the remaining meat sauce and sprinkle the rest of the mozzarella cheese on top. Cover and cook on low for 4-5 hours or until noodles are tender.
6. Let the lasagna rest for 15 minutes before serving. Garnish with fresh basil if desired.