Chilling and resting
Chilling and resting is the practice of refrigerating pastry dough between stages of work so that the fat firms up and the gluten relaxes, making the dough easier to roll and less likely to shrink in the oven.
Rest freshly made dough for at least 30 minutes before rolling, and rest a lined tin again before baking. The first rest lets the flour hydrate fully and the gluten slacken; the second firms the fat so the crust holds its shape when the heat hits it.
Skipping the rest is the most common cause of pastry that shrinks down the sides of the tin or slumps at the rim. Wrap the dough tightly so it does not dry out, and if it comes out of the fridge rock hard, give it 10 minutes at room temperature before rolling.