Step 1

Line a 9-inch square baking pan with parchment paper, allowing paper to overhang on the sides (for removal of the shortbread).

Step 2

In a medium bowl, whisk together the oat flour, potato starch  and salt.

Step 3

In a large bowl, cream together (I used a wooden spoon) the margarine and coconut sugar until blended and somewhat fluffy. Add the oat flour mixture, stirring until combined (it may look slightly crumbly).

Step 4

Press dough evenly and firmly into prepared pan. Prick with a fork. Loosely cover with plastic wrap and chill at least 1 hour or up to 1 day.

Step 5

Preheat oven to 325F.

Step 6

Bake in the preheated oven for 40 to 45 minutes until shortbread is cooked through and pale golden. Cool completely in pan.

Step 7

Using paper overhang, carefully remove shortbread from pan; place on cutting board. Cut into 4 quarters; cut each quarter in half, then in half again, making 16 rectangles total.