Preheat the oven to 350F. Line an 8 by 8-inch baking dish with 2 pieces of parchment paper so it hangs over all 4 sides.
For the crust, whisk together the flaxseed meal and hot water in a medium bowl and let sit 3 minutes.
Add the hazelnut flour, arrowroot starch, cinnamon, and salt to a large bowl and whisk to combine. Cut in the vanilla, coconut oil, and flaxseed mixture with a fork or pastry cutter. Press the mixture into the bottom and about ¾ to 1-inch up the sides of the prepared pan. Bake the crust 10 minutes.
Toss together the dark chocolate, walnuts, and flaked coconut in a large bowl and spread it out in the par-baked crust. Pour the sweetened condensed milk evenly over the top.
Bake until bubbling in the center, about 25 to 30 minutes; remove from the oven and sprinkle the sea salt on top.
Let the cookie bars cool completely (I let them sit overnight) before slicing.
Notes
Chocolate: Use stevia-sweetened chocolate to keep this paleo, and use as dark as you like it based on your preferred level of sweetness.
Recipe by An Edible Mosaicâ„¢ at https://www.anediblemosaic.com/paleo-hello-dollies-cookie-bars-vegan/