Blend the oats in a blender to create a flour. (See this link for detailed instructions)
Combine the oat flour, spelt flour, baking powder, coconut sugar and salt in large mixing bowl.
Add the butter and break into small pieces with a pastry cutter. Alternately, you may pulse the dough in a food processor.
Add the milk and incorporate by hand just until a dough forms. You will know it is done when you hold a small piece between your two fingers and it sticks together. You want to be able to see small chunk of butter because they will form layers when you are baking the crust and make it nice and flaky.
Wrap in plastic wrap and refrigerate for one hour or up to 2 days.
Remove from the refrigerator. Let sit at room temperature for 5-10 minutes to soften just enough to make rolling out easier.
Roll the dough with a rolling pin on a lightly floured surface to a 12-inch circle; about 1/8 of an inch thick. As you roll out the dough, check if the dough is sticking to the surface below. If necessary, add a few sprinkles of flour under the dough to keep the dough from sticking.
Carefully place onto a 9-inch pie plate. Gently press the pie dough down so that it lines the bottom and sides of the pie plate.
Use a pair of kitchen scissors or knife to trim the dough to within 1/2 inch of the edge of the pie dish.