1 pound Italian sausage
1 large (1 cup) onion, chopped
1 small (1/2 cup) green bell pepper, chopped
2 teaspoons finely chopped fresh garlic
2 (24-ounce) jars pasta sauce
1 (15-ounce) container ricotta cheese
3/4 cup grated Parmesan cheese
1 teaspoon Italian seasoning
1/2 teaspoon salt
1 (6-ounce) package (3 cups) fresh spinach leaves, chopped
12 no-cook lasagna noodles
Generously spray 6-quart slow cooker with no-stick cooking spray; set aside.
Combine Italian sausage, onion, green pepper and garlic in 12-inch skillet; cook over medium-high heat, stirring occasionally, 6-10 minutes or until sausage is cooked through. Drain, if necessary. Add pasta sauce; mix well.
Combine all filling ingredients in medium bowl until well mixed.
Spoon 1/4 meat mixture (about 2 cups) into prepared slow cooker; top with 3 lasagna noodles (break to fit). Spread with 1/4 cheese filling (about 3/4 cup); top with 3 cheese slices. Repeat layers 2 more times. Top all with remaining noodles; remaining filling and remaining meat mixture.
Cover; cook on Low heat setting 4-6 hours or High heat setting 2-4 hours, or until noodles are tender.
Top with remaining 3 cheese slices. Let stand until cheese is melted. Cut lasagna into pieces or wedges.
Prepare meat sauce and cheese filling the night before. Assemble lasagna in slow cooker the next morning and cook.