Preheat oven to 400oF. Line a 12×17 baking sheet with parchment paper.
Dissolve baking soda in warm water.
Combine oats, flour, salt, and brown sugar. Stir to combine, breaking up any lumps of brown sugar.
Stir in oil until well mixed.
Add baking soda/water mixture. Stir well.
Using your hands, form the dough into a ball.
Press the dough out on the baking sheet. Roll or pat dough out until about ⅛-inch thick. The dough should fill the baking sheet.
Using a bench scraper or pancake turner, score the dough into 24 squares (4×6) by pressing down into the dough.
Bake 15 minutes or until outer oatcakes begin to brown.
Using a sharp knife, cut along the score lines in the baked dough.
Allow to cool completely. Oatcakes should be crisp when cooled. If not, bake them longer next time.
Store in an airtight container.
