Whisk together the water, brown rice sourdough starter, melted butter, honey, and eggs until everything is well-combined.
Mix in the flax seed and the psyllium seed husk and allow to sit for 2 to 3 minutes to set up.
Add the flours and sea salt and mix well with a wooden spoon for several minutes.
Cover bowl with a plate or damp towel and allow to sour for 8-18 hours, or overnight.
Prepare a baking sheet by buttering or applying parchment paper.
Divide dough in two and sprinkle a work surface with tapioca flour.
Knead one ball of dough for several minutes, adding an additional ¼ to ½ cup of flour as needed.
Mold the dough into a round and place it on one half of the baking sheet.
Cut three parallel slashes into tops of dough with a sharp knife.
Let rise in a warm place for 2-4 hours.
Preheat oven to 400°F.
Bake for 25-30 minutes or until an internal temperature of 190°F is reached.
Move immediately to a cooling rack and cool at least 45 minutes before slicing.
