I'm pretty sure this recipe made enough to feed an army! (Should have invited company over.) It turned out really well, so I'll share the recipe with you. Let me know if you make yours a different way!
Brown ground beef (I used 1 lb.) and drain. Add chopped onion and garlic. Add cans of tomato sauce (I used three). Season with basil and oregano (fresh or dried). Simmer on low.
Place a ladle-full of sauce in the bottom of your slow cooker. Make sure the bottom is covered.
Break uncooked lasagna noodles to fit in crockpot and layer over the sauce.
Spread ricotta cheese over the noodles. On top of this, layer fresh spinach and other veggies as desired (I'd like to try mushrooms next time).
Top with shredded mozzarella cheese.
On top of this, pour more meat sauce.
Continue layering in this order (noodles, ricotta, spinach, mozzarella, sauce) until you reach the desired amount of layers. End with noodles.
Over all, pour 1/4 cup of water (I put the water in an empty tomato sauce can and swished it around before pouring over).
Cook on high for 4 hours (or less). You may need to push the top noodles down towards the end of the cooking time if they are curling up or too dry (yes, it's okay to open your crockpot to do this).
Top individual pieces with a sprinkle of mozzarella cheese.
If you make this in a 6.5 qt. crockpot like I did, expect this to feed 10-12 people!