I found this recipe on Cooks.com and just substituted in GF graham crackers made by Kinnicnick. It turned out pretty good, for me it was a little salty, but everyone else really liked it.
Graham Cracker Pie Crust
1 1/4 cup graham crackers, crushed
2 T. sugar
1/2 t. salt
6 T. butter, melted
Mix together and press into a 9in pie pan. Chill 1 hour before filling or bake at 375 for 7 mins. for a more crunchy crust.
Cool before filling.