In a food processor, process the oats and sugar until the oats are reduced to a fine powder, about 2 minutes. Add the flour and salt and pulse to combine. Add the butter and pulse 4 or 5 times, until the mixture resembles coarse crumbs.
In a small bowl, stir together the ice water and egg yolk. Add the egg mixture to the food processor in a slow stream and pulse until the crumbs begin to cling to the side of the processor bowl and hold their shape when pressed together.
Turn the dough out onto a lightly floured work surface. Using your hands—and a little muscle—form the dough into a 5-inch disk. Wrap it in plastic wrap and refrigerate it for at least 1 hour or as long as 24 hours.
On a lightly floured work surface, roll the dough into an 11-inch circle. Working quickly and carefully, transfer the dough to a 9-inch pie dish. Tuck the dough into the pie dish, using your fingertips to make sure that the edge of the pie is smooth and even. Refrigerate for 20 minutes.
Preheat the oven to 350°F (176°C).
Remove the pie dish from the refrigerator. Line the crust with aluminum foil or parchment paper, making sure to cover the edges, and fill it with dried beans or pie weights. Bake for 15 minutes. Rotate the crust and bake for another 15 minutes, or until the sides are somewhat firm and hold their shape.
Remove the foil and weights and bake for 6 minutes, or until the bottom of the crust looks dry and the crust is a very pale golden color. Let the crust cool while you make the filling. Leave the oven on.