Prepare the Dough (first rise):

1. In a large mixing bowl, whisk to combine sourdough starter, water, and salt until the starter dissolves.
2. Add flour and mix well to combine, scraping down the sides of the bowl (there should be no dry flour particles visible). Cover the bowl and let the dough rest for one hour. Resting helps build gluten strength naturally.
3. Apply some water on your hands and stretch and fold the dough in the bowl by folding the edges over to the centre, one edge at a time. Wet hands make it easier to work with the dough and it should take you less than a minute to fold over all 4 sides. Cover with plastic wrap and let the dough rest for 30 minutes. 
4. Stretch and fold the dough again, cover, and let dough rest until it almost doubles in size. It takes about 4 to 6 hours for the dough to double in size, depending on the room temperature (but it can take up to 8 hours if the room temperature is very cold). Since ciabatta dough is extremely wet and sticky with over 80% hydration, a couple sets of stretching and folding plus resting will be sufficient to build gluten strength, which results in chewy and tasty ciabatta bread.

Shape the Dough (second rise):

1. Transfer the dough to a floured surface. Note that the dough will still be very sticky and that is okay. Sprinkle dough with a little flour and shape it into an approximate 8x12-inch rectangle by gently pulling the dough from underneath. The dough should be soft and pliable. Be careful not to press down on the dough because the air holes trapped inside might get squeezed out.
2. Gently roll the dough into a log and press the edges to seal. Sprinkle some flour if the dough gets too sticky at any point. Cut the rolled dough in half using a bench scraper and place them a few inches apart on a well-floured surface. Sprinkle flour over the dough to prevent it from sticking, and cover with cling wrap.
3. Let the dough rest for about 1 hour until puffy (second rise). The dough should be filled with air bubbles inside.

Bake the Ciabatta Bread:

1. Carefully slide each dough onto a parchment-lined baking sheet pan with a bench scraper. Sprinkle flour to help with handling it and slowly stretch the ends a bit to shape the dough into approximately 12-inch loaves. Set aside.
2. Fill a deep baking pan with water and place it at the bottom of your oven. Preheat the oven to 420 F, and allow it to fill with steam from the water. When the oven is ready, slide the baking sheet pan in and spray some water with a spray bottle over the dough immediately. Bake for 20 minutes until the crust turns golden brown.
3. Let the bread cool for 20 minutes. To check if the bread is done, you can tap the bottom of the bread with your finger. The bread will sound hollow when done.