Preheat oven to 450°F. Blend flour, xanthan gum, and salt. Cut in shortening until crumbly; add water mixing with a fork until dough is moistened. Using your hands, form dough into a ball and lightly dust with gluten free flour. Place dough between two sheets of wax paper and roll out a large enough circle to hang over the edge of pie plate. Carefully remove the top sheet of wax paper and flip the crust into the pie plate. Remove remaining wax paper. Flute the edges of the dough on pie plate rim and prick dough several times with a fork to avoid puffing during baking. Bake until light brown, about 8-10 minutes. Cool on wire rack.
Note: Pie shell may be baked with filling in it, without pre-baking shell, if desired.