Preheat the oven to 450°F and line a baking sheet with parchment paper.
Whisk together the oat flour, all-purpose flour, cornstarch, baking powder, baking soda, and salt in a large bowl. Whisk for at least 20 seconds to be sure everything is well incorporated. Set aside.
Whisk together the yogurt, milk, olive oil, and maple syrup.
Pour the wet mixture into the dry mixture and stir it using a large spoon until the dough comes together, and be sure to scrape the bottom of the bowl. Flour your hands and form a ball with the dough. If your dough is too dry to form a ball, add more milk, one tablespoon at a time. If your dough is too wet, sprinkle a little more flour.
Place the dough onto a floured work surface. Using your floured hands, pat the ball of dough into a rectangular shape that's about 1" thick. Fold it into thirds like a letter and press it out again to 1" thick. Do this folding and pressing out method twice more, being careful not to overwork the dough. Use a round biscuit cutter to cut the dough into circles. I used a 2 ½" cutter. Carefully press the scrap dough together, pat it down to 1", and cut more biscuits. You may have a little scrap dough left over. Or, to avoid leftover dough scraps, you can cut the dough into squares using a sharp knife.
Place the biscuits on the prepared baking sheet. Bake for 11-13 minutes or until the tops of the biscuits are lightly golden brown. To enhance browning, brush the tops of the biscuits with milk before baking.
Remove from the oven and allow them to cool. Enjoy!