First of all get your levain ready:
To 150g warm water (25-29C) add 150g plain flour and a large tablespoon of your starter. Leave covered with a cloth on your worktop to work for about 6 hours. It should double in that time. Test if ready by dropping a teaspoonful into a glass of water. If it floats then it is ready to start.
For 2 loaves of bread:
760g organic NO. 4 white flour
135g khorasan flour
180g sourdough starter
670ml warm (25-29C) water
50g milled linseeds
30g chia seeds
50g toasted pumpkin seeds (could swap these for sunflower or whatever mix you prefer)
Mix water, sourdough levain and flour in a large bowl then rest for approximately 1 hour.
Soak the linseed and chia seeds together in a bowl of hot water. Approximately 100 -150ml of water.
After 1 hour is up. Add salt to the dough and mix in well with your hands till smooth.
Rest 30 minutes.
Now is the time of the bulk fermentation. For the first 3 hours fold the dough for 10 folds (stretch and fold over working around the dough in the bowl) every 30 minutes. After the first hour, incorporate the seeds into the dough.
After 3 hours, put the dough, covered in its bowl, into the fridge for 2 hours.
Take out the dough and preshape in to 2 loaves.
Rest for 20-30 minutes before the final shaping.
Put into bannetons lightly floured with gluten free flour and leave on the worktop for 30 minutes before placing covered in the fridge for 10-12 hours.
Take out of fridge for half an hour while oven and baking steel (or I use a large cast iron casserole dish and a pyrex casserole dish and have a shallow dish of water in the bottom of the oven for steam) are heating up to 230C.
When the oven is reading, take out your casserole dishes and tip your loaves in and quickly score the top with your lame knife (I use a Wire Monkey). Immediately put the lids on and into the oven at 230C for 25 minutes.
After 25 minutes, take the lids off and keep on baking at 220C for 25-30 minutes.
Take out of oven and leave 1 hour before cutting.
Timings very much depend on your oven. I use a fan assisted Rangemaster electric oven.