In a medium bowl, combine 300g of the water with the chia seeds and stir. Immediately, the chia seeds will start absorbing the liquid and within 30 minutes you will have a thick gelatinous liquid. This chia gel will help keep the bread moist.
While the chia gel is maturing, combine the flours, rye flakes, salt and yeast in a large bowl.
Add the chia gel and the remaining water (115g).
Knead for 10 minutes.
Place the dough back into the bowl and cover with a lid. Rest for about an hour at room temperature.
Deflate the dough and shape into a round loaf on a lightly floured work surface.
Prepare a proofing basket and place the loaf into the floured basket for its second rise. Cover with a polythene bag to keep the moisture in. Depending on the temperature in your room, the second proof may take approx. 1 or 2 hours. The fully proofed loaf will have expanded significantly.
Preheat the oven to 220°C for about 20 minutes.
Turn out the loaf onto a baking tray lined with baking paper or onto the preheated La Cloche baking dome (as I did for the loaf in my photo).
Bake for 10 minutes at 220°C before decreasing the temperature to 200°C and bake for another 45 minutes.
Cool on a wire rack.