Combine the oat flour, all-purpose flour, sugar and salt in a mixing bowl.

Using a pastry blender or your hands, cut the butter into bits and combine it with the oat/flour mixture. Work until the pieces of butter are no larger than peas.

Sprinkle three tablespoons of the cold water over the mixture and toss to mix it in.

Form the mixture into a loosely formed ball. Add more water if needed to mold the dough.

Turn the dough out onto a floured work surface and gently knead into a ball.

Divide the ball into halves and shape each half into a 4 inch circle.

Wrap the dough in waxed paper or plastic wrap. Refrigerate for 30 minutes to 1 hour.

Return the dough rounds to the floured surface, roll out one of the discs of dough into a circle.

Turn the dough gently as you work. Center your pie pan upside down on the circle of dough and roll it out until it is about 2 inches larger than the edges of the pan.

Carefully transfer it to the pie pan, rolling it up onto your rolling pin to move it. You can also fold it gently into quarters and place the point in the center and unfold it over the pie pan.

Press the dough gently into the pan; trim away any excess dough, and patch any holes. Leave about 1/2 inch beyond the edge of the pie pan.

Fold the edges up and over and crimp edges using a fork or your finger. Refrigerate the crust until needed.

You can make in advance. Wrap the dough well in plastic and refrigerate for up to 3 days or freeze for up to 2 months.