Make sure your starter is fed and bubbly; feed the night before so you are ready to start in the morning.
If using levain, mill wheat berries, and mix levain ingredients in a small container, leaving for 5 hours at 77ish F, or longer if cooler.
Mix fresh wheat flour (43 g), bread flour (550 g) and 400 grams of water (100 grams set aside) mixing with hands until no dry bits are left. Cover for 2 hours with plastic or wet towel to autolyse.
When levain is ready, or after dough has autolysed, add salt, seeds and levain or sourdough starter. Add remaining water (about 100 g) but slowly as it may not all be needed.
Mix all ingredients together by hand, pinching and folding, until well incorporated. Cover.
During bulk fermentation (4 hours) give the dough 6 sets of stretch and folds, the first 3 in 15 minute intervals and the last 3 in 30 minute intervals.
Lightly flour your working surface and pour out the dough.
Shape into a rough round shape and leave for half an hour uncovered.
Shape dough into round or oval shape and put into floured proofing basket or banneton.
Cover with large plastic bag or tea towel and refrigerate overnight.
In the morning take out your loaves and set oven to 450°F.
Line Dutch oven with parchment paper and carefully transfer loaf over into it.
Bake for 20 minutes with lid on, then remove lid for another 30 minutes until loaf is a golden hue.
Cool on rack for 30 minutes.