How to Make It
In a small bowl, whisk the lukewarm water with the coconut sugar, yeast and the 1 1/2 teaspoons of olive oil. Let stand until foamy, about 5 minutes.
In a stand mixer fitted with the paddle attachment, mix both flours with the tapioca starch, walnuts, flaxseeds, salt and baking powder. Add the wet ingredients and mix on low speed until just combined. Cover the bowl with a kitchen towel and let stand at room temperature for 2 hours.
3. Preheat the oven to 375°. Grease a large sheet of parchment paper with olive oil. Scrape the dough onto the parchment and, using a generously greased rolling pin, roll out the dough to a 12-by-16 1/2-inch rectangle, 1/16 inch thick. Slide the parchment onto a large rimmed baking sheet and cut the dough into 2-by-3-inch rectangles. You will have about 32 pieces. Bake for 12 to 15 minutes, until the flatbreads are set and starting to crisp around the edges. Let cool.
Brown rice flour, buckwheat flour and tapioca starch can be found at Whole Foods and on amazon.com.