> 1 lb lean ground beef
> 1 (15 oz) container part-skim ricotta cheese
> 1 (10 oz) pkg frozen chopped spinach, thawed and squeezed very dry
> 2 cups shredded part-skim mozzarella cheese, divided
> 1 1/2 (24 oz) jars marinara sauce
> 1 (12 oz) no-boil lasagna noodles
Heat a greased 12-inch skillet to medium-high. Add the ground beef, season with salt and pepper, and cook until browned, 6-8 minutes. Drain any liquid. In a large bowl, stir cooked ground beef into marinara sauce.
In a medium bowl, combine the ricotta, spinach, and 1 cup mozzarella. Season with salt and pepper.
Into a greased 5- to 6-qt slow cooker bowl, spoon a thin layer of the meat sauce. Arrange 1 layer of noodles over sauce, breaking noodles to fit as needed. Spread 1 layer of ricotta mixture over noodles. Spoon some sauce over ricotta. Repeat layering with remaining noodles, ricotta mixture, and sauce, ending with sauce. Not all of the noodles will be used. Top with remaining 1 cup mozzarella.
Cover with lid and cook on low 4 hours until noodles are tender.