To a large bowl, add the cottage cheese, Parmesan cheese, egg, parsley, salt, pepper, and garlic. Stir together until fully combined.
Spray a 6 quart slow cooker with non-stick spray and pour approximately 2 cups of marinara sauce to the bottom.
Pour approximately 1/3 of the uncooked ziti noodles on top of the sauce.
Spoon approximately 1/3 of the cottage cheese mixture over the ziti.
Repeat two more layers, ending with approximately 1 cup of sauce over the top.
Cover and cook on LOW for 4 hours.
Thirty minutes before the cook time is up, open the lid, sprinkle the mozzarella evenly over the top and cook an additional 30 minutes without the lid.
Once the cook time is up and the mozzarella has melted, turn the slow cooker to WARM and let the pasta stand for 15-30 minutes to set up.