Preheat the oven to 350ºF. Grease an 8x8” square pan with coconut oil (I recommend lining the pan with parchment paper as well if your pan doesn't have a removable bottom).
Combine the maple syrup and coconut oil and whisk until fully combined. Stir in the coconut flour and salt until a smooth door is formed.
Press the dough into the prepared pan. Bake for 9-11 minutes, or until golden brown. Let cool completely.
For the filling, combine the coconut sugar, maple syrup, and coconut oil in a small saucepan over medium-low heat and whisk to combine. Bring to a low boil and let simmer for about 2-3 minutes and then remove from heat. Let cool slightly.
While it cools, whisk together the non-dairy milk, flax meal, arrowroot starch, vanilla extract, and salt in a small bowl.
Add the milk/flax mixture to the slightly cooled sugar mixture and whisk to combine. Stir in the pecans, cashews, sliced almonds, macadamia nuts and chocolate chunks.
Pour the mixture over the cooled crust and bake for 30 minutes.
Let cool completely, at least 2 hours, in the refrigerator before cutting into 16 squares.
If desired, chop and melt the remaining 1 oz. of chocolate and drizzle it over the bars. Sprinkle with flaky sea salt. Let set in the refrigerator. Store leftovers in an airtight container in the refrigerator.