Blueberry Galette (Dessert)

Mix the oat flour, tapioca flour, psyllium husk powder, and sugar in a mixing bowl. 2. Use a fork or pastry cutter to cut the cold vegan butter into the mixture, then add the ice-cold water and mix again, adding a bit more water if the dough is dry or more flour if too wet. 3. Form the dough into a ball, wrap it in plastic wrap, and chill for at least 30 minutes in the refrigerator. 4. For the filling, stir together the blueberries, lemon juice, sugar, and tapioca flour in a medium bowl; set aside. 5. Preheat the oven to 390 degrees F (200 degrees C). 6. Divide the dough into 4-5 portions, flour a large piece of parchment paper with tapioca flour, and roll out each dough ball with a floured rolling pin into a circle. 7. Transfer the parchment paper to a baking sheet, divide the blueberries among the pies leaving a 1 to 1.5-inch border, and carefully fold the borders over the filling, overlapping when needed. 8. Brush the edges with oil or melted vegan butter and sprinkle with sugar. 9. Bake until the berry filling is bubbly and the crust is golden brown, about 25-30 minutes.