In a frying pan, brown the ground beef. Once the ground beef has browned, remove then sauté the onions. Next, add the ground beef back in once the onions are soft and stir in the tomato sauce. Save a little for the top of the lasagna to the side.
In the crockpot, place a layer of the ground beef. Layer with the ground beef, lasagna noodles, ricotta cheese, mozzarella cheese, ground beef, then repeat. You'll need to break up some of the lasagna noodles to get them in the crockpot, I wish there was another.
You'll get about 3 layers including the bottom layer. The top should be just lasagna noodles. Spoon the any leftover meat and the sauce you place to the side on top. Cover that with cheese. Then, pour some water around the sides of the crockpot lasagna. Place the lid on and cook on high for 4 hours.
When finished you can garnish with fresh basil, allow to cool, serve and enjoy.