Make the crust: In a large bowl, whisk together flour, sugar, and salt. Add cold butter cubes and cut in with a pastry cutter or fork until the mixture resembles coarse crumbs with some pea-sized pieces remaining.

Drizzle in ice water 1 tablespoon at a time, tossing with a fork after each addition, until the dough just begins to hold together when pressed. Divide dough in half, shape each into a disk, wrap in plastic, and refrigerate for at least 1 hour or up to 2 days.

Preheat oven to 400°F (200°C). In a large bowl, toss blueberries with sugar and let sit for 15 minutes to release juices. Stir in cornstarch, lemon juice, lemon zest, and cinnamon until the berries are evenly coated.

On a floured surface, roll one dough disk into a 12-inch circle about 1/8-inch thick. Transfer to a 9-inch pie dish, letting excess drape over the edges. Pour the blueberry filling into the crust, spreading it evenly.

Roll out the second dough disk and cut into 10 strips about 3/4-inch wide. Arrange 5 strips parallel across the pie filling, spacing them evenly. Fold back every other strip halfway, lay one strip perpendicular, then unfold. Repeat this weaving pattern with remaining strips to create a lattice.

Trim the lattice strips and bottom crust overhang to 1 inch beyond the pie dish rim. Fold the edges under and crimp decoratively. Brush the lattice with egg wash and sprinkle with coarse sugar.

Place the pie on a baking sheet and bake for 20 minutes. Reduce oven temperature to 350°F (175°C) and continue baking for 40-50 minutes until the crust is deep golden and filling is bubbling thickly through the lattice.

Cool the pie on a wire rack for at least 4 hours before slicing to allow the filling to set completely. The pie is best served at room temperature.