Please ignore if using shop brought pastry. Otherwise, follow the steps below.
Put the flour and salt in a large bowl and add the cubes of butter.
Use your fingertips to rub the butter into the flour until you have a mixture that resembles coarse breadcrumbs with no large lumps of butter remaining. Try to work quickly so that it does not become greasy.
Using a knife, stir in just enough of the cold water to bind the dough together.
Wrap the dough in clingfilm and chill for 10-15 minutes before using.
Alternatively using a food processor, put the flour, butter and salt in the food processor and pulse until the fat is rubbed into the flour.
With the motor running, gradually add the water through the funnel until the dough comes together. Only add enough water to bind it and then stop.
Wrap the dough in clingfilm as before and chill for 10-15 minutes before using.