Add flour, xanthan gum, sugar, and salt.
Whisk them together in your large bowl.
This helps distribute everything evenly.
Make sure there are no lumps.
Add your cold butter cubes to the flour.
Use a pastry cutter to blend.
Work until mixture looks like coarse crumbs.
Small butter pieces create those flaky layers.
Beat the egg in a small bowl.
Add ice water and vinegar to the egg.
Pour this mixture into your flour mixture.
Stir gently with a fork.
Mix until dough starts to come together.
Don't overmix or crust becomes tough.
The dough should be slightly crumbly.
Press it into a ball with your hands.
Wrap dough tightly in plastic wrap.
Put it in the fridge for 30 minutes.
This step is very important.
Cold dough rolls out much easier.
Place dough between two parchment paper sheets.
Roll it into a 12-inch circle.
Transfer carefully to your pie pan.
Trim edges and crimp as desired.