Preheat oven to 350°F. Line a baking sheet with parchment paper or silicone baking mat. Set aside.
Whisk the almond flour, tapioca flour, baking powder and salt together in a large bowl. Using a pastry cutter or 2 forks, cut in the butter or coconut oil until the mixture is crumbly. Set aside.
In a medium bowl, whisk the maple syrup, vanilla and almond extract together. Pour into the flour/butter mixture and gently mix together.The dough will be wet.Turn dough out onto prepared baking sheet and shape into a rectangle four inches high and 9 inches long. About 1/2 inch thick. Using a pastry brush, lightly brush the top and sides with egg wash.
Bake in preheated oven for 25-30 minutes, or until the top and sides of the biscotti slabs are lightly browned. Start checking the biscotti around 20 minutes and tent it with foil if it's looking too brown.
Remove from the oven, but do not turn off the heat. Allow the biscotti to cool for 10 minutes. Once the slab is cool enough to handle, cut it into 1-inch thick slices. Set slices cut sides upright, ¼ inch apart on the baking sheets. Return to the oven to continue baking for 8 minutes. Turn the biscotti over and bake for another 8-10 minutes or until the biscotti starts to brown around the edges.
The cookies will be slightly soft in the centers with harder edges. Remove from the oven and allow to cool for 5 minutes on the baking sheet. Transfer to a wire rack to cool completely before dipping in chocolate. The biscotti becomes crunchy as it cools. Save the baking sheets for the next step.