In a large bowl, place the flour, xanthan gum and salt, and whisk to combine well.
Pour in the olive oil and then the vinegar, and stir with a fork to combine.
Add ½ cup of cold water and stir until the flour absorbs the water, then mix or knead until the dough comes together.
If the dough is crumbly, add more water by the tablespoon, mixing after each addition, until the dough is smooth but not very wet to the touch.
Divide the dough into two equal parts (about 8 ounces each), flatten each into a disk and cover each tightly in plastic wrap.
Allow the dough to sit tightly wrapped at room temperature for 30 minutes to allow the flour to absorb the moisture of the oil and water.
Place each piece of dough between two pieces of unbleached parchment paper, and roll until it is about ⅛ inch thick (the thickness of a nickel).
The dough is ready to be draped over a souffle dish or pie plate filled with a thick, savory filling (such as chicken pot pie or vegetable stew), trimmed and cinched tightly.
Bake at 375°F until the crust is set and lightly golden brown. Serve immediately.