Source: https://www.powerhungry.com/2015/08/vegan-oat-shortbread-glutenfree/

Ingredients

• 3 cups oat flour
• 1/2 cup potato starch
• 1/2 teaspoon fine sea salt
• 1 cup (2 sticks) butter, softened
• 1/2 cup coconut sugar

Directions

1. Line a 9-inch square baking pan with parchment paper, allowing paper to overhang on the sides (for removal of the shortbread).
2. In a medium bowl, whisk together the oat flour, potato starch  and salt.
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).
4. Press dough evenly and firmly into prepared pan. Prick with a fork. Loosely cover with plastic wrap and chill at least 1 hour.
5. Preheat oven to 325F.
6. Bake in the preheated oven for 40 minutes until shortbread is cooked through and pale golden. Cool completely in pan.
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.