Does anyone have pointers on how to get big holes in the crumb? I know the
key is a very wet dough, but every time I do this (70-80 percent hydration)
the loaf kind of flattens out into a pancake and I don't get big holes.

Any tips on flours for this effect and/or mixing times and speeds?

My ideal by the way is the breads make by Sullivan Street Bakery in New York
City, if anyone knows the place.

Thanks, Sam