In a bowl, mix flour, salt, and sugar (if using).
Add cold butter and cut it into the flour until the mixture looks crumbly.
Slowly add ice-cold water, a little at a time, until dough forms.
Mix gently—do not overwork the dough.
Shape into a disk, wrap in plastic, and refrigerate for 30–60 minutes.
Roll out the chilled dough on a floured surface.
Place into a pie dish, fill as desired, and bake according to recipe.