In a bowl, mix together 150g active starter, water, and brown rice flour. Mix until smooth, and then cover and let rest at room temperature for anywhere between 4 and 18 hours.

Whisk together the psyllium husk, sweetener, and water. Whisk until combined and let gel while preparing the flour mixture.

In a large bowl or stand mixer, combine all of the flours + starches, plus salt.

Whisk the psyllium gel mixture into the preferment, along with the olive oil if using.

Add the wet ingredients to the flour mixture. Use a spoon and then your hands to bring the dough together, or use your dough hook to mix all of the ingredients until a smooth dough forms.

Once your dough is soft and smooth, turn it out onto a clean, smooth work surface. Knead into a smooth ball, and use your hands to shape the dough into a round.

Dust your banneton or tea towel-lined bowl generously with brown rice flour. Transfer the dough into your banneton, smooth side facing down.

Cover, and let the dough proof for about three to four hours at room temperature, or overnight in the refrigerator.

An hour before your dough is fully proofed, turn on the oven to 425°F. Preheat your Dutch oven inside the oven.

When your oven is preheated and your dough is well proofed, carefully flip the dough onto a sheet of parchment paper. Score the bread as desired.

Remove your hot Dutch oven from the oven. Carefully lower your loaf into the Dutch oven, replace the lid, and put your bread into the oven for 45 minutes.

After 45 minutes of baking, remove the lid and let it finish baking for 25 to 40 minutes.

Once the bread is golden brown to your liking, remove it from the oven and let cool completely at room temperature before slicing into it.