Prepare the Crockpot: Spray the crockpot with cooking spray or fit it with a crockpot liner.
Add the First Layer of Sauce: Pour about half of the pasta sauce into the bottom of the prepared crockpot, spreading it across the base.
Make the Cheese Filling: In a large bowl, combine the ricotta, 1 cup of the grated mozzarella, Parmesan, lightly beaten eggs, minced garlic, Italian seasoning, salt, and ground black pepper, mixing until the ingredients are evenly combined.
Fill the Shells: Spoon or pipe the cheese mixture into the jumbo pasta shells, filling them with the prepared ricotta mixture.
Arrange the First Layer: Place a layer of the filled shells into the crockpot over the sauce.
Add Sauce and Cheese: Spoon some of the remaining pasta sauce over the filled shells, then sprinkle some of the remaining mozzarella cheese over the top.
Repeat the Layers: Continue layering the filled shells, pasta sauce, and remaining mozzarella until the ingredients have been arranged in the crockpot.
Slow Cook the Shells: Cover and cook the stuffed shells in the crockpot for 4 hours, following the original slow-cooking method.
Garnish and Serve: Finish the cooked stuffed shells with fresh parsley for garnish before serving.