The amount of water required will depend on the dryness of the flour, relative humidity of ambience etc.

Sieve the flour and salt together, cut the butter into the flour and rub with your fingertips till it becomes fine breadcrumb consistency.

Add water and stir with a rounded knife until the mixture begins to bind together. Use your hand to knead lightly until the dough is formed.

To make a 'latticed' flan, use ¾ of this dough to make a base in the flan dish, and roll out, and cut into strips, the rest of the ball of dough.

See also Val's plain pastry recipe