Preheat oven to 350 degrees. Line an 8x8 or 11x7 baking pan with parchment paper.
For the base layer: In a mixing bowl, combine the almond flour, cornstarch, melted coconut oil, maple syrup, and salt. Using a fork, mix until you have a crumb mixture. Press the mixture into the bottom of the parchment-lined baking pan. Bake for 10-12 minutes or until golden brown. Remove from oven and let cool for at least 20 minutes.
For the middle layer: In a small saucepot, combine the tahini, maple syrup, brown sugar, coconut oil, vanilla, and a pinch of salt. Simmer over medium heat, continuously stirring, for 1-2 minutes or until the mixture is very smooth.
Pour the warm mixture over the cooked-based layer, smooth to cover the base layer, and place in the refrigerator for at least one hour so the middle layer sets.
For the top layer: Combine the chopped dark chocolate and one tablespoon of coconut oil in a microwave-safe bowl. Place in microwave and heat in 15-second intervals, removing and stirring, until the chocolate is completely smooth. Pour the melted chocolate over the firmed middle layer and smooth to cover. Sprinkle the melted chocolate with flake salt and refrigerator for at least 2 hours.
Once the bars have firmly set, pull the parchment paper from the baking pan, and cut the bars into desired size pieces. Serve immediately or store in the refrigerator until ready to serve. Bars can be frozen for up to two months.