Preheat the oven to 350F/177C. To make the crust, whisk together the coconut oil, honey, and vanilla extract in a large bowl. Add the almond flour, coconut flour, and salt. Stir together or use your hands to mix everything together, until you have a crumbly dough.
Pour the dough into an 8x8-inch baking pan lined with parchment paper. Use your hands to press the dough flat in the pan. Make sure it's pressed down very firmly.
Bake the base crust for 13-15 minutes in the oven, or until lightly golden on top and slightly darker around the edges, then remove.
The order of whisking the filling is important. Whisk the eggs and honey together in a bowl until smooth. Add the lemon juice and lemon zest and whisk again. Then add the tapioca flour and whisk again, until smooth, and no flour clumps remain.
Bake the lemon bars for 20-25 minutes, or until the center of the filling is set.
Let the pan cool on the counter for an hour, then transfer to the fridge and let cool another 2 hours before serving, to firm up. Slice into bars and serve plain, or with a dusting of powdered sugar.