Place flour and salt into the bowl of a food processor. Add the chunks of butter and pulse a few times, until the butter is incorporated in large pieces (about the size of a pea).
Slowly pour in the cold water while pulsing until a very crumbly dough is formed. Turn dough out onto a clean, lightly floured workspace and gently push it together with your hands – do not knead.
Rolling and folding the dough:
1. With a lightly floured rolling pin, roll out dough into a roughly triangular shape. Use your hands to fold the two bottom tips of the triangle inward and the top down, like an envelope.
2. Turn the dough a quarter-turn clockwise and roll out, again, into a rectangle this time. Fold the two ends lengthwise into the middle to meet. Then fold the dough in half across.
Turn the dough another quarter-turn clockwise, and repeat steps 1 and 2 above one more time, turning the dough a quarter-turn clockwise each time.
Wrap the puff pastry in plastic wrap and refrigerate until ready to use. Refrigerate for at least 45 minutes before using.