Two 10-ounce packages chopped frozen spinach, thawed
1 cup ricotta cheese
1 cup Parmesan cheese, divided
3 ½ cups jarred or homemade marinara sauce with ½ cup water stirred in
Six regular lasagna noodles
2 cups grated mozzarella
Squeeze the excess moisture out of the spinach. In a medium bowl, combine the spinach with the ricotta cheese, and stir to mix.
In another bowl, mix the marinara sauce with 1/2 cup water.
Spread 1 cup of the marinara sauce mixture in the bottom of a 6-quart slow cooker. Arrange two of the noodles in a single layer on top of the sauce, breaking the noodles as needed to fit. Spread 1 cup of the marinara mixture on top of the noodles. Dollop half of the spinach mixture on top of that, then top with ½ cup of the mozzarella. Add two more of the noodles, a cup of the marinara, the remaining spinach mixture, and another ½ cup of the mozzarella. Finish with the remaining two noodles, the remaining marinara, the remaining mozzarella, and the remaining ½ cup Parmesan.
Cover and cook on low for 3 to 3 1/2 hours, until the pasta is cooked and the cheese is melted and bubbling.