Spray your slow cooker with nonstick spray or line with a slow cooker liner.
Pour in half of a family size jar of marinara sauce.
In a bowl, add ricotta cheese, egg and parmesan cheese. Mix well.
If desired, cut up some fresh spinach and add to the cheese mixture.
Season with salt and pepper as well as a bit of Italian seasoning and garlic powder.
Transfer your cheese mixture from bowl to a ziploc baggie.
Cut a small hole in the corner of the bag.
Pipe the cheese into an uncooked manicotti shell.
Layer your shells over the sauce in the Crock-Pot.
Cover the shells with the remaining marinara sauce.
Cook on high for 2 hours.
Sprinkle the mozzarella cheese on top of the pasta and cover and cook for an additional 30 minutes.
Enjoy!