Help with custom walls facing inwards instead of outwards

I've created a custom wall using NorthWesTrees' tutorial and it works. However, my fence has an "outside" and an "inside" and the current procedures in place have all walls facing north or east. This is an issue because my wall has leaf coverings but I don't want the coverings on the inside of the wall, only the outside. I've wasted a lot of time trying to figure it out on my own, so I would really appreciate it if someone could help steer me in the right direction as to how to make my walls automatically face outward. 

Thanks in advance!