In a large mixing bowl, whisk together your flour mixture and salt. Then add the cold butter.
Cut the butter into the flour using a pastry cutter, pastry blender, potato masher, or pulse it a few times in a food processor. You’re looking for pea-sized bits—this is what creates those flaky layers later on.
Stir in your active sourdough starter or sourdough discard. Add a few tablespoons of ice water at a time, just until the dough starts to come together. Don’t overwork it—too much water or kneading can make it tough.
Form the dough into a ball and flatten it slightly. Wrap it in a piece of plastic wrap or cling wrap, and refrigerate for at least 1 hour (up to overnight). This helps the gluten relax and keeps that flaky crust texture.
On a lightly floured work surface, roll out your sourdough pie crust dough with a floured rolling pin. For a single pie crust, fit it into your pie pan or pie dish, trimming any excess dough. For a double-crust pie, divide the dough in half—one for the bottom crust and one for the top crust.
If making a single crust pie, blind bake before filling. Line the crust with a piece of parchment paper and fill with pie weights or dry beans. Bake at 375°F for 15 minutes, remove the weights, then bake another 5–8 minutes until lightly golden.