In a big bowl, mix all ingredients for the preferment together. Make sure to have extra space for the sourdough to rise.
For 12 to 24 hours, or overnight, let the bowl rest in a warm(ish) place.
When it's bubbly and smells sour-fruity, it is ready to use.
TIP: alternatively, mix all the preferment ingredients together with the rest of the bread ingredients, and leave the whole mixture to ripen overnight!
Mixing and resting
Roughly grind all the seeds and flakes using a spice/coffee grinder or food processor. Chop up the cranberries. Leaving some bits allows for great texture!
Combine all ingredients, including the ripened preferment to make the dough.
Let rest for 10 minutes, then transfer into a lined loaf tin and smooth the top with a spatula.
Cover with extra seeds. Leave to rest for 1 hour.
Baking
Bake at 175°C (350°F) for 90 minutes.
After 45 minutes in the oven, cover with another tin or foil.
When the full 90 minutes are up, take the bread out of the loaf tin and cool down on a wire cooling rack.
Notes
For substituting ingredients, helpful tips and step by step pictures, see the post above.