Add 110g Oat Flour, 90g Arrowroot Starch, 80g Brown Rice Flour, 15g Maple Sugar, and 11g salt to a stand mixer bowl and stir until combined.
Add the gelled psyllium mixture and 320g sorghum sourdough starter to the dry ingredients, then mix in a stand mixer with the dough hook until well combined.
Lightly dust your counter or a cutting board with sorghum or brown rice flour, then shape the dough into a ball.
Put the dough in a 7-inch banneton or other small bowl, then cover with a damp towel to let rise. This can be for 4-6 hours on the counter, or for 2-3 hours on the counter and then 8-12 hours in the fridge.
One hour before baking, preheat the oven to 475 degrees Fahrenheit - convection, with a Dutch Oven that will fit your bread inside.
After the oven has been preheating for an hour, score your bread as desired, adding brown rice flour if desired to make the score more obvious and decorative. Then, place it on parchment paper.
Take the preheated dutch oven out of the oven with oven mitts. Put the dough, with the parchment paper beneath it, in the dutch oven. Then, add 4 or 5 ice cubes that will turn to steam and quickly close the lid.
Put the Dutch Oven in the preheated oven and let it bake for 40 minutes at 475 degrees Fahrenheit convection.
After 40 minutes, reduce the temperature to 425 degrees Fahrenheit convection and let it continue to bake for another 20 minutes.
After 20 minutes, reduce the temperature to 375 degrees Fahrenheit convection, and remove the lid from the dutch oven so the crust can begin to brown. Bake for another 10 minutes.
Turn off the oven and crack the oven door, leaving the bread in the oven for an additional 10 minutes to dry out a bit more.
Remove the bread from the oven and use the parchment paper to lift it out of the Dutch Oven. Then, put it on a wire rack to cool 4-8 hours before slicing.
Tips & Alternatives
If you are not baking convection, increase the temperature of the oven by 25 degrees. This will just result in slightly less rise, but it will still be good.
If you do not have a Dutch Oven, instead preheat two baking sheets in the oven, one in the middle rack and one on the bottom. When adding the ice, add it to the bottom baking sheet, and put the bread on the middle baking sheet. Do not bake convection (see above) as the steam will leave the oven too quickly. You may want to cover the bread for a portion to prevent the crust getting too dark.
If you do not like the bottom of your bread to be darker, add uncooked rice to the bottom of your dutch oven underneath the parchment paper, at the same time as adding the bread.