In a medium bowl, combine almond flour, coconut sugar, ground flax, and salt. Add melted coconut oil, water, and vanilla extract to the dry ingredients. Stir with a spatula until the mixture comes together, forming a dough. Once combined, knead it gently with your hands for about 2 minutes until smooth and cohesive.

Place the dough between two sheets of parchment paper, roll it out to an even thickness of about ⅛ inch, and cut it into rectangular pieces measuring approximately 3.5 inches by 0.75 inches.

Transfer the cut rectangles onto a baking sheet lined with parchment paper and bake at 350°F (175°C) for 8-10 minutes until lightly golden on the edges. Let them cool on the pan for 5-10 minutes before transferring to a wire rack.

Once cool, mix melted dark chocolate and peanut butter until smooth. Spoon this mixture between two cookies, forming a sandwich.

Melt additional dark chocolate until smooth, dip each sandwich into the melted chocolate, and allow excess chocolate to drip off before placing on a wire rack.

Once the chocolate has set, store your Kit Kat bars in a sealed container. They remain fresh in the fridge for up to 2 weeks or can be frozen for up to 2 months.