Generously grease an 8 or 9-inch cast iron skillet or round cake pan with baking spray or oil.
In a small bowl, add 2 tablespoons of ground flaxseed and 6 tablespoons of water. Stir and allow to sit for about 5 minutes, until thickened. Meanwhile, make the almond butter.
In a blender or food processor, add in the 3 cups of sliced almonds and ¼ teaspoon salt. Process for about 3 minutes on medium speed, scraping down the sides as needed until a smooth almond mixture forms. This should yield just under 1 ½ cups of almond butter. Transfer to a mixing bowl or stand mixer.
Add maple syrup, baking soda, and flaxseed mixture. Mix for about 1 minute on medium speed, until combined. It will be a thick and sticky batter. Stir in chocolate chips.
Transfer batter to the greased skillet, use a spatula to evenly spread out the dough. Add extra chocolate chips on top of the cookie dough.
Bake in the center of the oven for 22 to 24 minutes, or until the surface is a light golden brown. Allow it to cool slightly before serving.
Notes
You can substitute the maple syrup with honey. The ground flaxseed "eggs" can be replaced with two large eggs. If making the cookie skillet vegan, paleo or gluten free, make sure the chocolate chips meets those requirements.