The morning before or at least a few hours before, feed the sourdough starter.
In a medium bowl, add active sourdough starter and water. Stir well to combine well.
Add the flour and salt, mix together till well combined.
Cover with a damp towel, and let rest for 1 hour.
Uncover and gently pull the edge of the dough near the side of the bowl and push it down into the middle of the bowl. Rotating and tucking (3 times).
Cover with a damp towel and let it rise for 8 to 10 hours.
Uncover and gently place the dough onto a lightly floured surface. Tuck all the edges into the center. Flip the ball dough over. Let it rest for 5 to 10 minutes.
With floured hands, gently cup the dough and move it around in a circular motion to tighten the shape.
Dust the tops and sides of the shaped sourdough generously with flour. Place the sourdough into the proofing baskets upside down, so the seams from shaping are on top and cover with a damp towel.