This is pastry as made by my mother and grandmother (and almost certainly great-grandma Collins too), hence the imperial measurements. These are what I grew up using, and the numbers just seem sort of easier. All you actually need to remember is half fat to flour, and keep everything cold. The fat should be a combination of butter, to give a good flavour, and lard or vegetable shortening [e.g. Trex or white Flora] to give a delicately short, crumbly texture.
For enough pastry to line a 23cm flan tin:
Sift the flour and salt in to a large bowl, add the cold, cubed butter and shortening and stir aroubd very briefly. Plunge your fingertips into the flour, pinch and lift. Rub your fingertips over the pads of your thumbs, with light, quick strokes, letting the flour and beads of fat fall through them back into the bowl as you do so. This is rubbing the fat into the flour.
Continue until there are no lumps of fat left, and you have a bowl of pale sand, with maybe the odd little flattened beady bit. If at any point your hands start to get very warm, pause and rinse them well under a cold tap to cool them again; similarly, if it feels like the fat may be getting warm and oily, put the bowl in the freezer or fridge for a few minutes to chill out. These precautions should prevent your pastry coming out greasy or heavy. Once the fat and flour are combined, add three tablespoons of cold, even iced, water and mix with a round-bladed knife. Using your hands, test to see if the pastry will clump together to form a delicately cohesive ball. If not, add another tablespoon and mix again with the knife. Keep on in this fashion until you have a dough which is firm, and will just about hold together without feeling damp or sticky. Too much water will make the pastry more likely to shrink, and the texture will be harder once cooked.
Either wrap the pastry in clingfilm and leave to rest in the fridge for 30 minutes* or roll out immediately. If the latter, you will have to let the pastry rest once it is in its tin and before cooking. (Resting is another anti-shrinkage ploy.) Preheat the oven to 200°C.
Starting with a round but flattened ball, roll the pastry out on a flat suface, lightly dusted with plain flour. Use only the gentlest pressure and keep turning the pastry through 90 degrees to keep the shape approximately round. You want a disc which is of the same thickness throughout, without any cracks or holes. You may have to do a bit of patting back into shape if it starts to deviate too far from circular (square-ish is fine, a long rectangle is not). Stop once you have a sheet just large enough to line your flan tin (check by sitting the tin on top of it). Place the rolling pin across the centre of the pastry disc, and gently lift one edge and drape over it. Carefully lift the rolling pin, using this as a support to transfer the pastry sheet to the tin. Ease into place, gently pressing into the crenellations if you have a fluted tin (as I do, though don't tell the WI, as savoury tarts and quiches are supposed to made in a plain mold according to their guidelienes I believe, and I don't want to be run out of town by an angry mob of jam-ladle brandishing grandma's dressed in tweed). Fold the excess over the edge of the tin and either roll the rolling pin over the top or press down with your hands to cut it off. If any cracks or holes have appeared, or the pastry doesn't quite reach the top of the tin in any places, patch up with the left-over bits that you have cut off.
If you didn't allow the dough to rest before rolling it out, place the tin in the fridge for half an hour now, otherwise proceed immediately. What follows is known as baking blind - i.e. empty. Line the pastry case with a piece of kitchen foil, then weigh down with baking beans. These can take the form of dried pulses, rice or even coins, or you could buy specially made ceramic ones in a kitchen shop - the point is having some small dry things spread over the foil-lined pastry so that it can't bubble up as it cooks. The same pulses or whatever can be used indefinitely, but be sure never to confuse them with fresh ones and cook them to eat.
Bake your lined pastry case in the oven for 10 minutes, until the sides are beginning to dry out, but not colouring at all. Take it out of the oven and remove the foil together with the blind beans. If the sides have started to colour, turn the oven down to 180°C, and fold little strips of foil over the edges of the tin. Bake for another 10-15 minutes, by which point the base should be dried out and turning a pale yellow. Remove from the oven and voila! A pastry case, which you can use immediately, or leave to cool before storing in an air-tight box for a couple days.
*or even for a couple of days, if it's easier to make it one day and use it another. It depends on how efficient and organised you're feeling. If the dough has been in the fridge for any length of time above an hour you will have to let it sit for a few minutes to soften a little before you can roll it out.