I've written rather extensively about the science of pie dough, as well as on common pie crust myths that need to go away, so I won't bore you with another 5,000 words on the subject. Instead, I'll give you the short version of the story, followed by a full-on, step-by-step illustrated version you can follow along with in the kitchen. It's an essential holiday skill that everyone should have in their pocket.
My pie dough is a little different from most pie doughs out there, and it all stems from the fact that the internal structure of a pie dough is not butter-coated-pockets-of-flour, as has been suggested in the past, but is in fact flour-coated-pockets-of-butter. It was this realization that led me to the technique I use: fully incorporating butter and flour into a flour/fat paste, then adding some additional dry flour to break it up and provide avenues for gluten formation.
The resulting dough is significantly moister and more supple than a traditional pie dough, which makes it easy to roll out (seriously, it rolls like Play-Doh), and it consistently bakes up into a texture that is simultaneously tender and flaky.