Heat a heavy-based griddle or frying pan (without greasing it) over a moderate heat until a drop of water sizzles in it. Sieve the salt and flour together, and blend in the fat as you would for ordinary pastry. Add warm water slowly-the amount may vary with the type of flour used, but only by a teaspoon or two. Knead the dough on a floured board with floured hands until it is no longer sticky, but is not hard. Keep the dough covered with a warm, damp cloth. Take approximately 45g (1 1/2oz) dough at a time and knead, folding it back on itself to trap air for a few seconds. Now make it into a little ball and flatten it. Place the flattened ball on a floured board, and roll it out with a floured rolling pin until it is so thin that you can see the board through the pastry. Cut out the tortillas by placing a 23cm (9-inch) plate on the thin dough and cutting around it. Pick up each tortilla, lay it on your right hand and place it carefully on the moderately hot griddle or pan, making sure it is flat and has no folds. As it cooks it will thicken slightly and small bubbles will appear. Cook for about 40 seconds on one side and then turn it and cook it for about 30 seconds on the other side. When cooked it should feel heavy and floppy, soft and pliable. Stack the cooked tortillas together, wrapped in a clean tea-towel. Always eat them hot except when they have been fried, when they can be eaten cold if consumed within 4 hours.