Sprinkle the last layer with plenty of bechamel and a little of filling in order to obtain a homogeneous and soft layer. At this point the lasagna is ready to be cooked in the oven, but it can be stored it in the refrigerator, covered with foil, for up to 24 hours. When cooking it, put it in the oven (preheated) at 180 degrees for 30 minutes. After cooking, remove from the oven and serve in large slices.