Put the flour, water, and salt in a large bowl. Mix until combined and cover with a kitchen cloth. Leave this to rest while the starter ripens.
Once the starter passes the float test, usually after 5 or 6 hours, add to the well-hydrated dough.
Mix well, cover and allow the dough to rest for 20 minutes before stretching and folding the dough 3 or 4 times. Cover and repeat the stretch-and-fold sequence twice more at 20-minute intervals.
At this point, the bulk dough can be left to ripen for several hours at ambient temperature. As it develops it will rise, so the container needs to be large enough to accommodate the increase.
When you are ready to shape the dough, pull it from the container and divide the dough into 2 equal parts.
Shape the bread and place in a floured breadbasket (or improvise one with well-floured kitchen towels draped into a 1-quart bowl).
These can be slipped into a large plastic bag and held in the fridge for up to 24 hours before baking. Alternately, they can be left at ambient temperature for an hour or 2 and baked the same day. Preferences for the long, cold fermentation are valid. The acids from the sourdough starter break down the proteins in the wheat; this process makes the nutrients more available and the final bread more digestible. The flavor and keeping quality of the bread are also noticeably improved.
That said, a bake that starts and finishes on the same day still produces very delicious results.