This sweet oatmeal crust makes the perfect base for a variety of cookie bars.
Heat the oven to 350º, then butter a 13- by 9-inch pan and set it aside.
Cream the softened butter, sugar, and salt in a large bowl with a wooden spoon. Stir in the oats, then stir in the flour a third at a time, rubbing in the last bit of it by hand to make coarse crumbs. Sprinkle on the water and rub briefly.
Press the dough into the pan, spreading it evenly into the bottom and very slightly up the sides. Chill the pan for 15 minutes. Then bake the pastry on the center oven rack for 15 minutes. Transfer the crust, in the pan, to a wire rack to cool thoroughly.