In a large mixing bowl, conbine flour, sugar and salt. Cut in butter until mixture resembles fine crumbs. Pat into an ungreased 38 cm x 25 cm x 3 cm baking pan. Prick all over with a fork. Bake at 325' for 35 minutes or until center is set. Cook for 10-15 minutes. Cut into small squares. Continue to cool to room temperature. If Cooking for two: Cookies will keep in a storage tin or airtight container for several weeks. ----