If you don't feel like making the tomato sauce or the cream sauce, you can substitute an already made marinara and a prepared alfredo to make this more quickly. You can make the spinach and ricotta filling up to 4 hours ahead and store it in the refrigerator in an airtight container. The assembled, unbaked lasagna will keep for at least a day in the refrigerator or you can freeze it up to 4 months (if it's wrappped tightly in plastic). Thaw the lasagna in the fridge and bring it to room temperature before baking. Recipe courtesy of Fine Cooking. And boy is it ever fine.