Combine the flour, salt, and sugar, if using, in a large bowl. Work the butter into the flour with a knife, pastry cutter, or your fingers until the mixture there are both large chunks and pea-size bits of butter throughout. Sprinkle the ice water onto the crumbly dough and, with your hands, push the dough from the sides to the middle of the bowl to form a ball that holds together. Transfer to a clean work surface. Cut the dough in half, place half on top of the other, and press down. Repeat the cutting and pressing steps three or four times until all of the water is incorporated into the dough and it clings together.
On a floured surface, gently flatten the ball of dough with a rolling pin. Starting from the center, roll the dough into a circle that is approximately 10 inches in diameter and ⅛-inch thick. Carefully roll dough over onto the rolling pin and transfer to the pie dish. Crimp the edges and fill, parbake, or bake as the recipe suggests.
To store the dough, form into two discs and wrap in plastic. The dough will be good for up to 2 weeks in the refrigerator.
To make in a food processor
Cut the butter into ½-inch pieces and place them in the bowl of the food processor. Add the flour, salt, and sugar (if using). Process until the ingredients are well-incorporated and butter is in both large and pea-size chunks. With the processor on, add the water a tablespoon at a time until the dough begins to clump but is still crumbly. Continue to drizzle a little water and pulse the food processor, stopping to test the dough with your fingertips to see if it is moist enough to hold together.
When you can gather the dough into a ball, remove it from the processor, place it on a lightly floured surface, and roll out and fit into the pan or store, as instructed above.