Combine flour, sugar, and salt; cut in shortening with pastry blender until mixture resembles coarse meal. Stir in oats. Sprinkle water (1 tablespoon at a time) evenly over surface; stir with a fork until dry ingredients are moistened. Shape into a ball; chill. Roll dough on a lightly floured surface to fit a 23 cm pieplate. Place in pieplate; trim off excess pastry along edges. Fold edges under and flute. Prick bottom and sides of pastry generously with a fork. Bake at 220ºC or 10 to dozen ----