They can't fill it if it's not on the hive!
Undrawn foundation is fine, it does not attract wax moths nor does it give small hive beetles a place to hide. I was told to add one box at a time of foundation, under the current box being drawn with a couple frames that are being worked or are capped from the first box swapped into the new one. On strong flow they will draw it out pretty fast, and I'm thinking of putting yet another box on my big strong hive since they are running out of room. Swarmed last week though, so they may slow down some.
If they don't draw it out and fill it, they may chew it some, but that won't hurt. They will accept it better next year since it has propolis on it and smells more like a hive even if they don't do anything with it this year.
Peter