There are a few ways to make sure that you keep from boiling over and ending up with pie filling all over the bottom of your oven. 1) You want to not overfill the pie crust, make sure you leave a little room at the top. Don’t have the filling going far over the top edge of the crust. 2) I always suggest placing a baking sheet directly under the tin or dish you’re using to bake your pie or on the shelf below it. This helps in case the pie filling boils over, it will catch the liquid and keep it from creating a terrible mess and smell. Just remove and wash at the end.