Preheat the oven to 350 degrees and grease a 9-inch cast iron skillet with coconut oil or butter.
In a small bowl, whisk together the flour, baking soda, and salt. Set aside.
In the bowl of a stand mixer, mix the coconut oil, eggs, maple syrup, and vanilla extract until well-combined.
Add the dry ingredients to the mixing bowl in 2 batches, and mix well after each addition to fully incorporate the flour. You’ll need to scrape down the sides a couple times.
Stir in the chocolate chips.
Transfer the batter to the prepared skillet. Press down with a spatula or your fingers to even out the batter.
Bake for 20 to 30 minutes, depending on how “done” you want it. The top will be set at around 20 minutes, but the inside won’t be cooked through. It will become more cake-like between 25 and 30 minutes. Insert a toothpick in the center, and when it comes out clean, it’s cooked through (but not as ooey-gooey as it was five minutes ago).