Blend rice flour, salt, and shortening in bowl. Set aside
In a small bowl, with mixer or a small whisk on low speed, gradually add potato flour to water
Pour the potato flour mixture over the rice flour mixture and work in with spoon
Then knead into a ball with as few strokes as possible. Either press across bottom and upside of your pan or roll between 2 pieces of wax paper that is dusted with rice flour
Flute edges and use for un-baked crust or bake and then fill with filling.
