In a large skillet over medium heat cook the sausage, onion until brown. Add the garlic and cook for 1 minute. Add the tomato sauce, tomato paste, water, salt, and oregano and stir until well incorporated.
Layer bottom of slow cooker with 1 cup of sauce. Add a layer of noodles to fit in pan, meat sauce, layer of spinach, ricotta cheese. Repeat layering 2 more times. Top with remaining sauce and then the shredded mozzarella cheese.
Cook on low for 3 hours.
Disclaimer
Please note that the nutritional information provided are guidelines and may vary based on the brand of products used. For your specific nutritional goals use My Fitness Pal or Verywell Fit recipe calculators. All content within this site is not intended as medical diagnosis or treatment and should not be considered a substitute for professional medical expertise.