Cook beef, garlic, and Italian seasoning in a large nonstick skillet over medium-high heat until beef is browned, stirring to crumble. Drain; set aside.
Combine pasta sauce and water in a small bowl; set aside.
Place 4 uncooked noodles in a 4-quart electric slow cooker coated with cooking spray, breaking noodles to fit. Layer with half each of beef mixture, pasta sauce mixture, and mushrooms. Spread ricotta cheese over mushrooms. Sprinkle with 1 cup mozzarella cheese. Layer with remaining noodles, meat, pasta sauce mixture, and mushrooms. Sprinkle with remaining 1/2 cup mozzarella cheese. Cover with lid; cook on high-heat setting 1 hour.
Reduce heat setting to low; cook 5 hours.