In a food processor, add the almond meal, rice flour, tapioca flour, arrowroot flour, sugar, salt, and xanthan gum. Process for a few seconds to incorporate these ingredients. Add coconut oil, and pulse through briefly to begin to break up and incorporate. Then, add milk, a few tablespoons at first (for double crust; one tbsp at a time for single), pulsing through, and then one tablespoon at a time after that, pulsing through until the dough has just come together and has started to form a ball (doesn’t have to be one unified ball, just until some of the dough has started to come together).
Remove dough from processor and shape into a ball. For the double-crust, divide the dough in two (you can weigh each half if you like for precision, but it’s not necessary). If the dough has become warm, shape into a flattened disc, wrap in plastic wrap, and refrigerate for about 20-30 minutes. (You can also refrigerate this dough for a few days before using, and remove from fridge for an hour or two before rolling, long enough for the coconut oil to soften again in the dough).
When ready to use, place flattened disc between two sheets of parchment (for easiest rolling). Roll the dough out to about 2- 2 1/2” larger than your pie plate (see note). Place bottom crust in greased (see note) pie plate.
Place crust in freezer for 15-20 minutes while preparing filling (ex: Apple Pie, p.), or prebake crust (see note) if you will be using a no-bake filling in the pie.
For a double-crust, roll out the second-half of dough, place over top of filling, and crimp edges (don’t trim edges, the baked crust is too tasty, and even if thicker in spots, is still fabulous, so keep things rustic).
Follow directions for specific pie filling, and if using double crust, it’s a nice idea to brush the top with a little non-dairy milk and sprinkle a little sugar over top.