I have found by making many, many pie crusts that as PriFi stated, you can handle the dough all you want, until you add water. Also, as she stated, the water has to be ice cold. The dough doesn't have to be ice cold. But if the house temp. rises above 77' F., the lard will begin to liquify, which will destroy the flakiness of the end crust.
Think about what you are making. Your initial dough is a combination of fat, flour, and salt, that will form a bunch of little pea-sized chunks. These are bound together by a little ice water, whose temperature keeps the chunks from blending together.. When the dough is rolled out, it flattens these little chunks of dough into thin flakes, again just barely held together by that little bit of wet starch. Without that little bit of water, there is nothing to hold the little chunks together, and the dough is unmanageable. You can roll it out, and it will look great. When you try to transfer it from the table to the pie pan, it falls apart.
For a standard 2 crust pie, place 3 cups of flour into a large mixing bowl, along with 1.5 tsp. of salt. Start adding lard, about a cup at first. Cut the lard (or shortening) into the crust. As the flour and fat mix, they will begin make little pebble sized chunks of dough. If there is not enough fat, there will be loose flour hanging around in the bowl. When the amount of fat is correct, all of the flour and fat will be combined, and will form pebble sized lumps in the bowl. It is at this stage that you add the ice water. The water will combine with the starch to make the dough stick together enough to work with.
Too much water will make the dough too wet and gooey, again ruining the dough. So add the ice water a little at a time, sprinkling it all over the dough. I add about an 8th cup of ice water. Gently fold the dough together until it forms a single dough-ball. Divide the ball into two halves.
Roll out the first ball on a well floured working surface. I also flour the top of the dough, which I have flattened into a rough disk with my hands. Push the rolling pin from the center to the edges, in all directions. When you think your dough is rolled out enough, place your pie pan on top of it, inverted. The dough should be three inches larger than the pan.
With a sharp knife, cut a smooth circle around the pan, 2 inches larger than the pan. This will allow you to pick up the dough without it breaking.
Slide a icing knife under the dough to loosen it from the table. Then Either use a rolling pin to lift and wrap the dough around, or fold in half, then again in half. Place the point of the resulting triangle in the center of the pan and unfold it. Gently press it down into the pan edges.
I usually brush my bottom crust with egg wash and place into a 400' oven for five minutes to set the egg. This keeps the bottom crust from getting soggy from the filling.
Roll out the top crust to the same size as the bottom crust. Loosen it from the table and fold like with the bottom crust, or cut into strips to make a woven crust.
Fill the bottom crust, and place the top crust on top. Fold the excess between teh bottom crust and the pan sides. Flute the edges. Brush the top with egg-wash, and sprinkle with sugar. Cut small vent holes into the top crust to allow steam to escape, and bake for 50 minutes to an hour at 375' F. or until golden brown.
This method has never failed me, and gives me the flakiest, most tender crusts imaginable.
Hope it helps.
Seeeeeya; Chief Longwind of the North