Use a 6-quart slow cooker sprayed with cooking spray. In a large skillet on the stovetop, brown the ground meat and drain any accumulated grease. Add the jar of pasta sauce to the meat and retain the jar (don’t rinse it!).

Spoon some of the meat and sauce mixture into the bottom of your slow cooker. Add a layer of dry lasagna noodles (you may have to break them to get a good fit).

Smear some of the ricotta cheese on top. Add a handful of sliced mushrooms, some spinach leaves, and half of the sliced mozzarella. Add another spoonful of the meat and sauce mixture and repeat the layers until the slow cooker is full. Top with shredded cheese.

Put water into the empty pasta sauce jar, seal it, and shake. Pour the contents over the assembled ingredients. Cover and cook on low for 6-8 hours or on high for about 4 hours. You may need to poke the noodles down into the sauce an hour or so before serving so they don’t get too crispy on the sides.