Whisk together brown rice flour, tapioca starch, potato starch, psyllium husk powder, and salt in a large bowl.
In a separate bowl, combine the active sourdough starter, warm water, olive oil, honey, and apple cider vinegar.
Pour wet ingredients into dry ingredients and stir until a thick, sticky dough forms.
Let the dough rest for 30 minutes to allow the psyllium husk to fully hydrate.
With wet hands, shape the dough into a round loaf and place on a parchment-lined baking sheet or into a proofing basket dusted with rice flour.
Cover and ferment at room temperature for 4–8 hours (or refrigerate overnight) until the dough has risen by approximately 50%.
Preheat oven to 425°F (220°C) with a Dutch oven inside.
Score the top of the loaf with a sharp blade. Transfer to the hot Dutch oven.
Bake covered for 30 minutes, then uncover and bake 15–20 minutes more until deeply golden and the internal temperature reaches 205–210°F (96–99°C).
Cool on a wire rack for at least one hour before slicing.
