Preheat your oven to 350ºF and have a 9-inch pie dish ready. (No need to grease it.)
In the bowl of a large food processor fitted with an "S" blade, add in the oat flour, tapioca starch, salt, and coconut oil. Secure the lid and press the "pulse" button several times until the coconut oil has disappeared into the flour. The mixture should look like a crumbly flour. (If you have a pastry cutter, you can use that instead of the food processor.)
Add in the maple syrup and cold water, and pulse the mixture again until the dough comes together. It's normal for it to stick together and start to form a ball. Be careful not to run the food processor for too long, as you don't want to warm up the coconut oil. As soon as it looks like pie dough, you're done with the mixing part!
Lay a large sheet of parchment paper on your counter and place the ball of dough in the middle of it. Lay another large sheet of parchment paper over the dough ball and press is down with your hands to start to flatten out the ball into a crust.
Use a rolling pin over the top layer of parchment paper and roll the pie dough out until it's roughly 11 or 12 inches in diameter, to fill a 9-inch pie plate with room to go up the sides of the pan.
Once the crust is rolled out, remove the top layer of parchment paper. Carefully lift the crust up using the bottom piece of parchment paper and flip it over onto your hand. Use both hands to gently lower the crust into your pie pan and remove the parchment paper (that's now on top of the crust) once it's in place. You'll need to use your fingers to press the pie crust into the corners of the pan, and you might need to break off pieces of the crust that are overflowing from the edges. Feel free to use pieces of the dough to repair any holes-- just press extra dough into any spots that break. Use your fingers to flatten the edges of the crust for a smooth look.
For a pie that will be baked, like my vegan pumpkin or vegan pecan pie, this is the time to add your filling. This crust works very well for pies that need to cook for up to 45 minutes. At 55 minutes, the edges start to get too brown, so you might need to cover them if your recipe calls for a baking time that long.
For a cold pie filling, like my French Silk Pie, you can bake this crust on its own for 15 to 20 minutes, until lightly browned. Let it cool completely, then fill it!
*If you need this to be gluten-free, make sure you use oats that are labeled as "certified gluten-free" to avoid cross-contamination during the manufacturing process. To make your own oat flour, simply grind gluten-free oats in a blender or coffee grinder.