Whisk the oat flour, cornstarch, baking soda, and salt together in a large bowl. Set aside.
In a medium-size bowl, whisk the melted butter, coconut sugar, and granulated sugar together until no lumps remain. Whisk in the egg and vanilla extract until well incorporated.
Pour the wet ingredients into the dry with a large spoon or rubber spatula. Fold in the chocolate chips.
Cover the dough and chill in the refrigerator for an hour or up to overnight. If you refrigerate the dough overnight, let it sit out at room temperature for 10 minutes before baking to soften up.
Preheat the oven to 350º F and line two baking sheets with parchment paper or baking mats.
Using a cookie scoop (mine is about 1 and ½ tablespoons), scoop out balls of cookie dough and place them on your baking sheet, making sure to leave a couple of inches between each cookie.
Bake for 10-11 minutes or until the edges are very lightly golden. The centers will still be very soft but will firm up as they cool. Allow the cookies to cool on the baking sheet for 10 minutes before transferring them to a wire rack to cool completely. This is optional, but I like to press a few extra chocolate chips into the cookies when they are still warm on the baking sheet.
Enjoy!