Preheat the oven to 350°F
Place the lasagna in an oven-safe dish
Add a little water or sauce if it looks dry
Cover the dish tightly with foil
Bake for 20 to 30 minutes
Remove the foil for the last 5 to 10 minutes if you want the top to crisp
Check that the center is hot all the way through
Let it rest for a few minutes before serving