First, we will make psyllium gel. Combine psyllium husk and water in a medium-sized bowl and whisk to prevent clumping. Add the sugar to the bowl and set it aside for a couple minutes.

Combine the flour, starches, baking powder, and salt in a separate large mixing bowl and whisk to incorporate.

Now, add the sourdough starter to the bowl with psyllium gel and stir to combine.

Add the wet ingredients to the bowl with the dry ingredients and mix using an electric mixer with dough hooks or do it by hand. Mix until the dough comes together and all ingredients seem to have incorporated evenly. The dough will be sticky but workable.

Turn the dough over onto a lightly floured working surface and flatten it out. Dust the dough with extra flour if it is sticking to your hands too much! Fold each side of the dough onto itself, flip, and shape the dough into a ball.

Place the dough upside down into the banneton basket or a mixing bowl lined with a kitchen towel. Cover the bread with a tea towel to prevent it from drying out. Leave the loaf to ferment for 5-7 hours at room temperature (21-24C/60-75F) or for 12-18 hours in the refrigerator.

Once the bread is done proofing, transfer the loaf onto a piece of parchment paper and score in a pattern you like. Lower the parchment with the bread into a cold Dutch oven, cover with the lid, and place the Dutch oven into a cold oven. Start preheating the oven to 450F/230C and once it's preheated, start the timer for 40 minutes.

After 40 minutes, take the loaf out of the Dutch oven and transfer it to the oven rack. Lower the temperature to 350F/175C and bake uncovered for another 30 minutes. Once the bread is done baking, transfer it to a cooling rack and let it sit until no longer warm to the touch. Slice and enjoy!