Preheat oven to 375°F.

Combine potato starch, tapioca flour, millet flour, almond meal, sugar and salt in a food processor and pulse a few times to combine. Add butter and pulse again until mixture resembles coarse meal.

Add egg and pulse until completely combined to make a slightly sticky dough.

Turn dough out onto a large sheet of waxed paper dusted with potato starch.

Sprinkle potato starch over dough and knead gently, working in about 2 more tablespoons potato starch, until dough holds together without being sticky but is still very pliable.

Using your fingertips, press dough into a 10-inch circle.

Invert a 9-inch pie pan on top of the dough then quickly flip over both the pan and the dough so that the dough now rests in the pan.

Gently peel away and discard wax paper and press dough into pie plate, patching it together, if needed.

Crimp and trim the edges as desired then prick sides and bottom all over with a fork.

Line crust with parchment paper and fill with pie weights or dried beans.

Bake until crust is just set and slightly dry around the edges, about 15 minutes.

Remove parchment paper and pie weights, fill with pie filling and bake as needed.

Alternately, for a pie that requires a pre-baked crust, return to oven and bake until cooked through, about 15 minutes more.