Preheat the oven to 350°F and line a 9 x 9-inch baking pan with two overlapping parchment sheets. In a large mixing bowl, whisk together flax and 3 tablespoons water until smooth. Allow to sit for a few minutes to thicken before stirring again.
Add the salt, baking soda, pure maple syrup, vanilla extract, cornstarch, cocoa powder and coconut sugar to the bowl in that order. Whisk together until combined. The batter will be thick.
In a mixing bowl, combine the flour, corn flour, baking powder, salt and pepper. Add in the almond butter and mix thoroughly until it’s completely distributed. Don’t worry about overmixing; these are flourless. You’ll be left with a very thick and sticky batter after combining everything properly
Break the graham crackers sheets in half, then line the bottom of the dish with them–you should use about 4 1/2. Spread brownie batter on top of graham crackers until it covers them entirely and is level at the top. Bake 25 minutes or until edges appear firm; cool 30 minutes.
Allow the brownies to cool before changing the broiler setting to low. Next, place the marshmallows and chocolate chips on top of the brownie then put it under Low Heat for 5 minutes or until marshmallows are melted & golden brown in color. Lastly, take it out of oven; break graham cracker pieces on top (if desired).
Remove the brownies from the dish using the parchment paper and cut into individual squares. Serve right away or keep for up to 2 days in an airtight container.