In a large saucepan, begin by browning sausage. Once cooked, add onion and saute until tender, then cook garlic for 30 seconds. Drain off fat. Add pasta sauce, herbs, and ½ cup water (use your pasta sauce jar for extra flavor and no waste!) to the pan. Stir back in the strained sausage mix. Let simmer for 5 minutes, or until thickened over medium to low heat--season to taste.
While sauce is simmering, mix ricotta, 1 ⅓ cup mozzarella, parmesan, and egg--season with salt.
Spray your slow cooker with nonstick spray and ladle in about a cup of sauce. Our slow cooker held 3.5 noodles in each layer; yours may be different. Fit them in as close together as possible without overlapping, breaking noodles where necessary. Then do a layer of cheese, more sauce, noodles, and end with pasta. Use remaining sauce (½-1 cup) to top the pasta and sprinkle with remaining mozzarella.
Take 1 ¼ cup water and gently pour around the outside of the lasagna, cover, and cook on low for 2.5 - 4 hours. Let rest a few minutes before slicing.