Dough with big bubbles before shaping

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After my preferment and first rise, when I go shape my boules of sourdough, I always end up with fairly dense dough which has large pockets/bubbles, rather than a uniformly pillowy and fluffy dough.

 

Any advice? I'm using a mix of whole wheat and white flour, a mature levain starter, and mixing by hand with stretches and folds.

 

I'd like a texture more pillowy, like this!

 

https://www.youtube.com/watch?v=cIIjV6s-0cA

Important to know when the bulk ferment is sufficiently done. Not de-gassing the dough while doing stretch and folds will help. Each time the dough is de-gassed it'll make a tighter crumb. When shaping it is also important to not take out all the bubbles. Knock the big ones out and enough to handle the dough but don't de-gas fully. Also remember the higher the wholegrain the less fluffy the bread.