The flavor of the sauce is key. Keep it loud enough because it's paired with bland noodles and cheese. Also, the ratio of sauce to uncooked noodles in this crockpot recipe is important so that the noodles have enough moisture to cook, but not too much to be soupy at the end.
I subbed in spinach and mushrooms for the ground beef, but you could always add a few slices of sausage or pepperoni, or put in some bell peppers or olives.
Here the lasagna is served with homemade Italian bread and roasted, marinated Brussels sprouts.
Easy-Peasy Vegetarian Lasagna (I got the basic plan from Convenient Slow Cooker Lasagna in the Fix-it and Forget-it Big Cookbook)
1/2 lb. sliced mushrooms
1/2 lb. chopped fresh spinach
5 cups spaghetti sauce, the more herbs the better
12 oz. package uncooked lasagna noodles
3 cups grated mild white cheese, mozzarella is expected
1 1/2 cups ricotta cheese or cottage cheese
1/4 cup water (if your sauce is on the thin side, skip the water)
1. Grease the insert of a 6-quart crockpot.
2. Mix together the ricotta and grated white cheese. Set aside.
3. Put a little spaghetti sauce on the bottom of the insert. Put half the mushrooms on top. I put a few grinds of pepper in here.
4. Add a layer of noodles on top, breaking as necessary to fit them in, and covering the mushrooms as completely as possible.
5. Spread 1/3 of the cheese mixture over the noodles. Add some spinach, some sauce, more noodles, more cheese, etc. etc. Sprinkle in some dried herbs if you think your sauce is not assertive enough. I always use fennel with Italian tomato sauces. You'll use up all the stuff except for maybe a few noodles (I suppose you could work to fit them all in - what on earth do you do with a few random lasagna noodles hanging around? Maybe add another tablespoon of water if you use the whole box.). End the layers with sauce on top. Pour the water in at the edge so as not to disturb the layers. Sprinkle with Parmesan.
6. Clap the lid on the slow cooker, turn to high for 30 minutes, then low for 4 hours. Keep in mind that slow cookers do vary in temperature, so just keep an eye on it the first time you make it.