Brown ground beef and Italian sausage in a large skillet over medium-high heat, breaking up meat as it cooks, then drain excess fat.
In a medium bowl, combine ricotta cheese, eggs, 1 cup mozzarella, 1/2 cup Parmesan, Italian seasoning, garlic powder, and salt, mixing well.
Spray the inside of a 6-quart slow cooker with cooking spray, then spread 1 cup of marinara sauce on the bottom.
Layer one-third of the broken lasagna noodles over the sauce, then top with one-third of the meat mixture, one-third of the ricotta mixture, and one-third of the crushed tomatoes.
Repeat layers two more times, ending with remaining marinara sauce spread over the top layer.
Sprinkle remaining 1 cup mozzarella and 1/2 cup Parmesan over the top, cover, and cook on low for 4 hours until noodles are tender.
Turn off slow cooker and let lasagna rest for 15 minutes before serving, garnished with fresh basil.