MELT COCONUT OIL: Melt the coconut oil in the microwave until it is liquid. Measure a level 1/2 cup of oil once fully melted. Set aside to cool back to room temperature -- it should not be hot when adding to the recipe.
BLEND OATS: Add old-fashioned oats to a blender or food processor. Blend or process until the oats are fine and resemble flour, stirring and re-blend if needed so that ALL the oats are a fine powder. Measure the oat flour after blending and not before, to get a level and gently packed 1 and 1/2 cups of oat flour. Set aside.
WET INGREDIENTS: In a medium-sized bowl, combine the cooled coconut oil, vanilla extract, large egg, and brown sugar in a bowl. Briskly whisk everything together until completely smooth.
DRY INGREDIENTS: Add the oat flour, baking soda, cinnamon, and salt. Mix with a wooden spoon and stir until just combined; then stir in the dark chocolate chips.
CHILL: Cover the dough tightly and chill for 20-30 minutes. (Don't skip chilling, but don't chill longer than 30 minutes or the dough is almost impossible to shape!) Meanwhile, preheat the oven to 350 degrees F. Remove the dough and use a 1-tablespoon measuring spoon to portion out cookie dough balls. Tightly roll the balls and then slightly flatten. You should get 22-24 cookies from this dough. Place rolled-out balls on a parchment-paper-lined plate. Once rolled, chill all the cookie dough balls for another 10 minutes.
BAKE: Once chilled, transfer the cookie dough balls to a lined sheet pan, spacing them out 2-inches apart. Bake for 7-9 minutes (we think they're perfect at 8 minutes) or until no longer gooey looking on top. Slightly underbaking is best for flavor and texture. Carefully remove the tray from the oven. If desired, press a few more chocolate chips into the tops of the cookies. It makes them look pretty and ensures chocolate in every bite! Once those chips have melted a bit, add a sprinkle of sea salt onto the melted chocolate, if desired. Let the cookies stand on the sheet pan for 5 minutes. Then, very carefully, use a spatula to remove from the sheet pan to a cooling rack. Handle delicately-- these cookies are crumbly.
ENJOY/FREEZING LEFTOVER COOKIE DOUGH: Enjoy hot, warm, or at room temperature (we like them best right out of the oven!). Cookies are best the same day they're made -- they get harder and less sweet every day following. I recommend freezing the unbaked cookie dough rather than baked cookies. Drop the cookie dough balls on a large sheet pan and freeze until solid. Once solid, transfer the frozen cookie dough balls to an airtight container or bag and freeze for up to 3 months. To bake: Bake these cookies straight from the freezer. There is no need to thaw, but you may need to add an extra minute to bake time.