In a large skillet cook the Italian sausage, onion and minced garlic. Breaking up the sausage into crumbles and cooking until the sausage is cooked and no longer pink. Drain to remove excess grease and set aside.
In a medium bowl stir together the ricotta cheese, oregano, basil, parsley, egg and Parmesan cheese until well mixed. Set aside.
In the bottom of a 3.5 quart casserole shaped slow cooker add 1 1/2 cup of marinara sauce and spread it to cover the entire bottom of dish.
Lay down on top of the sauce 1 layer of uncooked lasagna noodles.
On top of the lasagna noodles spread half of the ricotta cheese mixture making sure it is evenly distributed.
Sprinkle a a layer of mozzarella cheese on top of the ricotta cheese.
Add a layer of the browned sausage, onion & garlic mixture.
Add a layer of marinara sauce.
Repeat layers - noodles, ricotta cheese, mozzarella cheese, sausage, sauce. Ending with sauce then a light layer of mozzarella cheese.
Cover crock-pot and cook on LOW for 6-8 hours.
Serve with a side salad and some crusty bread or garlic bread for a wonderful and easy dinner.
Notes
If you do not have a casserole Crock-Pot you can still make this recipe in a 6 to 6.5 quart or round slow cooker. You will just need to break up your noodles to make them fit as a layer since it is kind of hard to make rectangular shaped noodles fit neatly inside a rounded shape.