Place flour, sugar, and salt in a food processor and pulse a few times to combine. Add the cold grated butter into the food processor and blend until a dough begins to form (about 15 seconds).
Scrape down the sides of the food processor if needed and continue to pulse. Dough will look crumbly at this point.
Add water into the food processor and blend until dough starts to come together and create large clumps / a dough ball (about 15 seconds).
Pour dough out onto a lightly floured worksurface. With floured hands, work the dough just enough to create a ball. If ball is not forming, add cold water 1 Tbsp at a time as needed.
Flatten ball into a 1" rectangle, wrap in plastic wrap, and place in the fridge for a minimum of 2 hours (up to 5 days) before rolling out.
When ready to use, place chilled dough onto a floured surface and gently roll out with a floured rolling pin. Start from the center of the dough and work towards the edges. If you start to have cracks, piece back together with your hands and continue rolling. Roll out to about 2" larger in all directions than your jelly roll pan.
Roll dough onto rolling pin and transfer to jelly roll pan. Push into corners. Remove excess dough that folds over the top edge of the pan (you can do this easily by rolling your rolling pin along the edges, this will basically 'cut' the dough at the very top edge of your pan).
After filling is added, crimp edges with your fingers.