In a large bowl, whisk together the flour, salt, and sugar (if using).

Add the cold butter cubes. Using a pastry cutter, two forks, or your fingertips, cut/rub the butter into the flour until the mixture resembles coarse crumbs with some larger pea-sized butter pieces remaining (these create flakiness). For extra ease/flakiness, pulse in a food processor: Add flour/salt/sugar, then butter, and pulse 8–12 times until crumbly. Don't overprocess.

Drizzle in 6 tablespoons (85g) of ice water. Stir gently with a fork (or pulse a few times) until the dough starts to come together. Add more water 1 tablespoon at a time only if needed—the dough should be shaggy and hold together when squeezed but not sticky/wet.

Turn the dough out onto a lightly floured surface. Gently knead 2–3 times to bring it together (avoid overworking to keep it tender).

Divide into two equal portions (about 340g each). Flatten each into a disk, wrap tightly in plastic wrap, and refrigerate for at least 1–2 hours (or up to 3 days). This chills the butter and relaxes the gluten for easier rolling.

When ready to use: Roll one disk on a floured surface to about 12–13 inches diameter (for a 9-inch pie). Transfer to your pie dish. For lattice top, roll the second disk and cut strips.

Fill with your blueberry mixture, top as desired, crimp edges, brush with egg wash if you like (optional for golden color), and bake per your pie recipe (usually 425°F/220°C for 15–20 min, then lower to 375°F/190°C until bubbly and golden).