Brown the ground beef in a skillet and drain excess fat.
Add marinara sauce to the beef and mix well.
In a bowl, combine ricotta cheese with egg and mix thoroughly.
Spray the crockpot with cooking spray.
Layer uncooked lasagna noodles at the bottom.
Spread half of the meat sauce over the noodles.
Add half of the ricotta mixture on top of the sauce.
Repeat the layers with noodles, meat sauce, and ricotta.
Finish with a final layer of noodles and top with remaining marinara sauce.
Sprinkle mozzarella cheese on top and cover the crockpot. Cook on low for 4-6 hours.