Whisk the flour, sugar, and salt for the crust. Cut in the cold butter until pea-sized pieces remain, then gradually mix in 3 to 4 tablespoons ice water until the dough holds together. Form it into a disk, wrap, and refrigerate for at least 30 minutes.

Combine the flour, oats, brown sugar, cinnamon, and salt for the topping. Work in the butter until coarse crumbs form, then refrigerate the crumble while preparing the filling.

Mix the blueberries with sugar, flour or cornstarch, lemon juice, lemon zest, vanilla, cinnamon, and salt. If using frozen blueberries, keep them frozen rather than thawing them.

Roll the chilled dough into an approximately 12-inch circle. Fit it into a 9-inch pie plate, trim and crimp the edges, then refrigerate the shaped crust while the oven heats.

Add the blueberry filling to the cold crust and spread the crumble evenly over the berries. Place the pie on a foil-lined baking sheet to catch any bubbling juices.

Bake at 425°F (220°C) for 15 minutes. Reduce the oven to 375°F (190°C) and continue baking for 35 to 45 minutes, until the topping is golden and the filling visibly bubbles near the center.

Cool the pie on a rack for at least 2 hours before slicing. This resting time lets the fruit juices thicken and gives you clean, generous wedges.