Make the sponge: In a medium bowl, whisk together the water, starter, and teff flour until smooth. Cover with a kitchen towel and proof at around 75° to 80°F (24° to 29°C) for 3 to 8 hours, until it has a mousse-like texture when you run a spoon through it.

Make the dough: In a stand mixer, stir together the oat flour, sorghum flour, tapioca starch, and salt. Add the active sponge to this bowl. In the same bowl you used to make the sponge, combine the flaxseed and psyllium. Pour in the water while you simultaneously whisk until smooth. Let it gel for 5 minutes. Add this gel to the bowl with the flour. Add the maple syrup. Snap the dough hook onto the mixer and mix the dough on medium speed until it is smooth, 2 to 3 minutes. The dough should feel moist and bouncy and hold its shape.

Add the sunflower, pumpkin, and white and black sesame seeds. Continue mixing on medium speed until the seeds are well distributed throughout the dough, about 1 minute. Transfer the dough to your work surface and knead it a couple of times. Shape it into a tight ball.

Cover the dough with seeds: Place a handful of mixed sunflower, pumpkin, and white sesame seeds on a plate and dip the top of the dough to coat. The surface of your dough should be fairly moist so the seeds will stick to it, but if that is not the case, spray the dough with a little bit of water before dipping it into the seeds.

Proof the dough: Lightly dust a proofing basket with some oat flour and place the dough in it upside down so the seed-coated surface is on the bottom and the seam of the dough is on top. Cover the proofing basket with a kitchen towel. At this point, you can proof your dough at room temperature for 1½ to 2½ hours or do a cold fermentation in the refrigerator anywhere from 10 to 20 hours. If you decide to proof the dough in the refrigerator, it is best to cover the basket with plastic wrap tightly secured with a rubber band so the surface of the dough doesn't dry out.

Preheat the oven: About 45 minutes before your dough is ready, position a rack in the bottom third of the oven and place a 5.5-quart (5.2 L) cast-iron Dutch oven on the rack. Preheat the oven to 500°F (260°C). Once the oven has reached temperature, let the Dutch oven continue heating for 15 minutes.

Score the dough: When the dough is ready, lay out a piece of parchment on your work surface and carefully invert the dough onto the parchment. Score your dough (either one large score in the middle or a grid pattern on top).

Bake the bread: Carefully lift the dough along with the parchment and place both in the preheated Dutch oven. Add 2 or 3 ice cubes next to it. Cover with the lid and bake for 45 minutes. Remove the lid, reduce the oven temperature to 425°F (220°C), and bake for 10 minutes, or until the bread is dark golden brown.

Cool the bread: Transfer the bread to a wire rack and let it cool for at least 30 minutes before cutting into it. Be patient, it pays off. Store the bread at room temperature wrapped in a paper bag for up to 2 days.