Gather all ingredients.
Preheat the oven to 325 degrees F (165 degrees C).
Beat butter and brown sugar together until smooth and creamy.
Add 3 to 3 ¾ cups flour; mix well.
Sprinkle board with remaining flour. Knead for 5 minutes, adding enough flour to make a soft dough.
Roll out dough to ½-inch thickness. Cut into 3x1-inch strips.
Prick shortbread cookies with a fork and place on ungreased baking sheets.
Bake in the preheated oven until edges are golden brown, 20 to 25 minutes. Cool on the baking sheet briefly before removing to a wire rack to cool completely.
