Mix the ricotta, spinach, artichokes, egg, 1/2 cup Parmesan, garlic powder, salt and pepper.
Spread 3/4 cup marinara over the bottom of a greased 6-quart slow cooker.
Break three noodles to fit over the sauce without letting their edges touch the bare crock.
Layer one-third of the ricotta mixture, 3/4 cup marinara and 1/2 cup mozzarella over the noodles, then repeat twice.
Finish with the last three noodles, remaining marinara, remaining mozzarella and remaining Parmesan.
Cover and cook on low until a knife slides through the center noodles and the filling reaches 165°F, 4 to 4 1/2 hours.
Turn off the cooker, uncover and rest the lasagna for 25 minutes before cutting into portions.