Cook onion in 10-inch skillet over medium heat 6 to 8 minutes, stirring occasionally, until onion is translucent.
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 sauce 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 sauce mixture.
Top with 5 noodles, remaining cheese mixture and one-fourth of the sauce mixture.
Top with remaining 5 noodles and remaining sauce 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.
If preparing as a freezer meal - Simply place all ingredients into a freezer safe bag except for your tomato sauce and 1 cup of mozzarella cheese. Freeze. When ready to cook thaw in the refrigerator overnight and place into the slow cooker. Add sauce and reserve cheese until the last 10 minutes.