Preheat the oven to 350 °F. Prepare a large cookie sheet (or 2 smaller sheets) by lining with a silicone mat or parchment paper.
In a large bowl or a stand mixer, cream together the butter and sugars. Add the egg and vanilla and mix until well combined. Add the baking soda and salt and combine. Then mix in the oat flour until fully incorporated. Fold in the chocolate chips.
Scoop the dough into 1 and ½ to 2 tablespoon balls. Place the balls onto your prepared baking sheet and lightly squish them down so they are a bit wider than tall (about ½ inch or 1 cm thick).
Bake (one cookie sheet at a time) for 8-11 minutes until the edges are set and very lightly browned. The centers will still be soft.
Let the cookies cool on the baking sheet for 5 minutes before using a spatula to move cookies to a wire rack to cool completely.
Notes
Make AheadThe cookie dough can be made up to 3 days ahead and refrigerated. It can also be rolled into balls and frozen for up to 3 months. When ready to bake, bring the dough to room temperature and follow the directions for baking.LeftoversOnce completely cooled, store leftover cookies in an airtight container at room temperature for up to 4 days or freeze for up to 3 months.