It’s best to first slap and fold the dough without adding all the reserved water to get the dough smooth and strong.
If you’re a fan of the slap & fold mixing technique I’ve described in the past, you can do this but be aware that it is difficult at this hydration. It’s best to first slap and fold the dough without adding all the reserved water to get the dough smooth and strong. Then, return the dough to the mixing bowl and slowly add the remaining water while folding the dough.