Line the bottom and sides of a 9 - inch square baking pan with parchment paper; cut off excess parchment paper around top edge of pan. (myrecipes.com)
If you are having a problem with the liquid boiling over, I have heard if you run some butter or coconut oil around the inner top edge of the pan, it keeps the mixture from boiling over. (naturalsweetrecipes.com)
Gently crimp the top of the foil sheets around the top edge of the pan. (simplyrecipes.com)