For the Crust
- 5 cups all-purpose flour, plus more for rolling
- 1 1/2 teaspoons coarse salt
- 2 tablespoons sugar
- 2 cups (4 sticks) cold unsalted butter, cut into small pieces
- 1 to 1 1/2 cups ice water
For the Filling
- 2 1/4 pounds fresh or frozen blueberries (8 cups)
- 3 tablespoons cornstarch
- 1/2 cup sugar
- 1 tablespoon grated lemon zest, plus 3 tablespoons lemon juice
- 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.