Add Italian sausage to a large skillet over medium high heat.
Cook until browned. If using pork sausage, you'll need to drain it once it's finished cooking. If you're using turkey Italian sausage, it won't need to be drained.
Add the spaghetti sauce to the cooked sausage and stir to combine.
In a separate mixing bowl, add the cottage cheese, parmesan cheese, egg, and Italian seasoning. Mix to combine.
Spray the slow cooker insert with nonstick spray.
Start by placing ⅓ of the meat and sauce mix on the bottom of the slow cooker. Spread it evenly.
Layer 3 lasagna noodles, breaking as needed to cover the sauce.
Layer half of the cottage cheese mix on top of the lasagna noodles.
Lay half of the mozzarella cheese.
Put the next layer of meat sauce mix (⅓ of original amount) and spread evenly.
Repeat steps 5, 6, and 7. Reserving a small amount of mozzarella for the top.
Top with remaining 3 noodles (breaking as needed to evenly cover).
Pour the remaining ⅓ of sauce on top. Topping with the reserved mozzarella.
Place the lid on the slow cooker and set it on low. Cook for 5-6 hours or until the pasta is tender.