In a mixing bowl, combine the oat flour, coconut sugar, and salt. Pour the melted coconut oil and beaten egg into the dry ingredients. Stir until the mixture comes together and forms a dough.
Press the dough into a 9-inch pie dish, making sure it covers the bottom and sides evenly.
In a large mixing bowl, combine the blueberries and lemon juice. Toss to coat the blueberries with the lemon juice. In a separate bowl, mix together the coconut sugar and cornstarch. Sprinkle the sugar mixture over the blueberries and gently stir to coat the berries evenly.
Pour the blueberry filling into the prepared oat flour crust. If you'd like, you can use any remaining oat flour dough to create a lattice or decorative topping for your pie.
Preheat your oven to 375°F (190°C). Place the pie in the preheated oven and bake for about 45-50 minutes, or until the crust is golden brown, and the filling is bubbling.
Allow the pie to cool on a wire rack for at least an hour before serving. Slice and serve your healthy blueberry pie. Enjoy!