1. Add the ground Italian sausage (or ground beef) to a large saute pan, and cook over medium-high heat until browned and cooked through, using a large spoon to stir and break up the meet into small crumbles as it cooks.  Remove from heat and drain off any excess grease.  Set aside.

Meanwhile, as the meat is cooking, go ahead and get ready to assemble the lasagna.  Begin by spraying the insert of a large 6-quart slow cooker with cooking spray.  Then layer the ingredients in the following order:

1. Spread 1 1/2 cups pasta sauce evenly along the bottom of the slow cooker.
2. Layer about 4 lasagna noodles — breaking them into smaller pieces as needed to fit — evenly over the sauce to cover the bottom of the slow cooker.
3. Layer about 1/3 of the ricotta cheese (a little over 1 cup) evenly on top of the noodles.  (I found it was easiest to do this in small spoonfuls, and then spread them out with a spatula.  It’s totally ok if it’s messy and uneven!)
4. Sprinkle 1/2 cup of the shredded Mozzarella cheese and 2 Tablespoons of the Parmesan cheese in an even layer on top of the ricotta.
5. Layer about 1/3 of the cooked ground meat in an even layer on top of the cheeses.
6. Layer about 1/3 of the chopped spinach in an even layer on top of the ground meat.
7. Layer 1 cup of pasta sauce in an even layer on top of the spinach.
8. Repeat with another layer of noodles, ricotta, Mozzarella/Parmesan, ground meat, spinach, and sauce.  Then repeat with another layer of noodles, ricotta, Mozzarella/Parmesan, ground meat, spinach, and sauce.  Then add one more layer of noodles, sauce, and Mozzarella.
9. Place the lid on the slow cooker and cook on high for 3-4 hours or on low for 6-8 hours, or until the noodles are tender.
10. Turn off the heat, and sprinkle the top of the lasagna evenly with the remaining Parmesan and fresh basil.  Serve immediately.  (Or if you let the lasagna sit and rest for 30 minutes, it will cut into pieces much more easily.)