Combine 100g of the refreshed sourdough (the rest goes back into the fridge for future bakes) with all the remaining ingredients (the soaker you prepared the day before and all of the main dough ingredients) and knead for about 10 mins. The dough will be sticky yet pliable.
Leave the dough to rest for about an hour.
Oil a bread baking tin and distribute a handful of sunflower seeds across the bottom of the tin, covering the surface evenly.
Transfer the dough into the oiled and seeded bread baking tin, evenly distribute the barley flakes across the top of the dough and cover with a lid or a polythene bag to keep the moisture in.
Rest until fully proofed (this takes a good 4 hours in my cool kitchen) and preheat the oven to 220°C in time.
Bake at 220°C for 10 mins, and at 200°C for a further 40 mins.
Leave to cool on a wire rack.