In a bowl, combine ricotta, Parmesan, 1 cup of the mozzarella, 1/4 tsp each of salt and pepper, and all the spinach.
In a pan over medium high heat, cook ground beef with garlic, oregano/Italian herbs, 1/2 tsp salt and 1/4 tsp pepper until no longer pink. Drain.
Add 1/2 cup of marinara to the bottom of a 5-6 quart crock pot and mix with half of the ground beef. Top with a single layer of noodles, breaking if needed. Layer 3/4 cup of marinara over noodles, 1/3 of the ricotta mixture over sauce, and half the remaining ground beef. Repeat with noodles, 3/4 cup of marinara over noodles, 1/3 of the ricotta mixture over sauce, and the remaining ground beef. Top with a layer of noodles, half of the remaining marinara, the rest of the ricotta mixture, the remaining marinara, and rest of mozzarella. Cook on low for 4 hours or high for 2 hours.