Preheat the oven to 350°F and line a 9 x 9″ baking pan with two sheets overlapping parchment paper cut to fit the pan. In a large bowl, combine flax with 3 tablespoons water. Stir together then allow to sit for a few minutes to thicken.To the flax mixture, add the salt, baking soda, pure maple syrup, vanilla extract, cornstarch, cocoa powder, and coconut sugar to the bowl in that specific order. Whisk together the ingredients until thoroughly combined. The batter will be very thick.Stir in the tahini and continue to mix until it’s fully and evenly distributed. Don’t worry about overmixing. It won’t hurt anything since these are flourless. After the mixture is thoroughly combined you will be left with a very thick and sticky batter. This is normal. Fold in 1/2 cup of the chocolate chips then transfer batter to the lined baking dish and spread out evenly to the sides. Place a few more chocolate chips on top, if desired.Bake in the oven for 25 to 30 minutes. Allow to cool completely before serving. The longer they cool, the better they hold together.