Prep: 1. Thaw and chop frozen spinach, squeezing to remove excess moisture. 2. Grate parmesan and mozzarella. Make: 1. In a bowl, mix together the spinach, ricotta, 1/2 cup of the parmesan and salt and pepper, to taste. 2. In a second bowl, mix together the marinara sauce and water. 3. Spread 3/4 cup of the marinara mixture in the bottom of a greased 4- to 6-quart slow cooker. 4. Top with 2 noodles (breaking to fit), 3/4 cup of the remaining marinara mixture, half the spinach mixture, and 1/2 cup of the mozzarella; repeat. 5. Top with the remaining noodles, marinara mixture, mozzarella, and parmesan. 6. Cover and cook on low until the noodles are tender, 3 1/2-4 hours.
You can use fresh spinach (about 24-30 ounces) if you want, we recommend blanching it first and then squeezing out any excess water so that the lasagna doesn't end up soggy. To blanch - boil water, add spinach for 1 minute and then drain and rinse in cold water. Check out our favorite tips for slow cooking here - http://blog.gatheredtable.com/2015/07/10/use-your-slow-cooker-all-summer-long/