Line a 9×9 baking pan with parchment paper and set aside.
In a large bowl, add the maple syrup, 1/3 cup SunButter, 2 tablespoons of coconut oil, and sea salt. Mix together well.
Add the oats, and stir until they are evenly coated.
Reserve 2-3 tablespoons of the oat mixture (save for topping the bars). Press the remaining oat mixture into the pan. Use wet hands to press it into the pan. A wet pastry roller also helps pack it down into an even layer. Set aside while making the chocolate layer.
Combine 1/4 cup of SunButter with 1 tablespoon of coconut oil. Stir well.
Use a double boiler (or a glass bowl over a pan with water) heated to a low boil. Add the dark chocolate chips and 3 tablespoons of the SunButter and coconut oil mixture. Reserve 2 tablespoons to swirl on the top.
Pour the melted chocolate on the oatmeal layer. Drizzle the remaining SunButter and coconut oil mixture over the top of the melted chocolate. Use the edge of a knife to run back and forth through the chocolate to swirl the SunButter.
Carefully break apart the leftover oat mixture to sprinkle across the top of the chocolate. Sprinkle mini chocolate chips (or cacao nibs) over the top if desired. Add a sprinkling of flaky salt if using (highly recommended!).
Cover the pan with foil and refrigerate the bars for 1 hour (or overnight). Pull the bars with the parchment paper out of the pan and place it on a cutting board. With a very sharp knife, cut into 16 bars.