1. Make crust: In a food processor, pulse flour, salt, and granulated sugar until combined. Add butter; pulse until mixture resembles coarse meal, with a few pea-size pieces of butter remaining. Sprinkle with 3 tablespoons ice water. Pulse until dough is crumbly but holds together when squeezed (if necessary, add up to 2 tablespoons ice water, 1 tablespoon at a time); do not overmix. Form dough into a disk, wrap tightly in plastic, and refrigerate until firm, at least 1 hour (or up to overnight).

2. Preheat oven to 375 degrees. Lightly flour a rolling pin and work surface and roll out dough to a 12-inch round. Place in a 9-inch pie plate, fold overhang under, and crimp edges. Make filling: In a large bowl, toss together peaches, brown sugar, and flour until combined. Make crumble: In a small bowl, combine brown sugar, flour, and oats; using your hands, work in butter until large clumps form.

3. Transfer peach filling to pie shell, then sprinkle crumble evenly over top. Place pie on a rimmed baking sheet and bake until juices are bubbling and topping is golden, 1 hour to 1 hour 15 minutes. Let cool on a wire rack 1 1/2 hours before serving.