Crock pot lasagna

1 pound bulk Italian sausage
1 medium onion, chopped (1/2 cup)
3 cans (15 ounces each) Italian-style tomato sauce
2 teaspoons dried basil leaves
1/2 teaspoon salt
2 cups shredded mozzarella cheese (8 ounces)
1 container (15 ounces) part-skim ricotta cheese
1 cup grated Parmesan cheese
15 uncooked lasagna noodles

Cook sausage and onion in 10-inch skillet over medium heat 6 to 8 minutes, stirring occasionally, until sausage is no longer pink; drain. Stir in tomato sauce, basil and salt.
Mix 1 cup of the mozzarella cheese and the ricotta and Parmesan cheeses. (Refrigerate remaining mozzarella cheese while lasagna cooks.)
Spoon one-fourth of the sausage mixture into 6-quart slow cooker; top with 5 noodles, broken into pieces to fit. Spread with half of the cheese mixture and one-fourth of the sausage mixture. Top with 5 noodles, remaining cheese mixture and one-fourth of the sausage mixture. Top with remaining 5 noodles and remaining sausage mixture.
Cover and cook on Low heat setting 4 to 6 hours or until noodles are tender.
Sprinkle top of lasagna with remaining 1 cup mozzarella cheese. Cover and let stand about 10 minutes or until cheese is melted. Cut into pieces