Make crust: In a food processor, pulse flour, salt, and sugar until combined. Add butter; pulse until mixture resembles coarse meal, with a few pea-size pieces of butter remaining. With machine running, add 1 cup ice water. Pulse until dough is crumbly but holds together when squeezed (if necessary, add up to 1/2 cup water, 1 tablespoon at a time). Do not overmix. Divide dough into 2 disks; wrap each tightly in plastic. Refrigerate until firm, at least 1 hour (or up to overnight).
Preheat oven to 400 degrees. Make filling: In a large bowl, toss together blueberries, cornstarch, sugar, and lemon zest and juice. On a floured work surface, roll out 1 disk to a 12-by-16-inch rectangle. Place in a 10-by-14-by-1-inch rimmed jelly-roll pan. Pour in blueberry filling, then lightly brush edges of crust with water. On floured surface, roll out second disk to an 11-by-15-inch rectangle and lay over blueberry filling; press along moistened edges to seal. Fold overhang under, tucking it into pan, and crimp edges. With a paring knife, cut slits on top to vent.
Place pie in oven, then reduce heat to 375 degrees. Bake until crust is golden and juices are bubbling, 50 minutes. Let cool on a wire rack 1 hour. Serve warm or at room temperature.
To freeze: Let this slab pie cool completely, then freeze it for up to 2 months. Thaw it at room temperature and reheat it in a 350-degree oven for 25 minutes.