In a large bowl combine the flour, oats and water into a shaggy, sticky dough and let it sit for 1-3 hours to hydrate.
Add in the sourdough starter, liquid honey and the salt and combine together using wet hands, into a sticky dough. Tip in a flat glass or ceramic dish and leave it to relax for 15 minutes.
Over the next three hours, stretch and fold this dough every 30 minutes, using a coil fold (see video.) Always use wet hands. It is normal for your dough to stretch back out after each fold.
Now leave the dough on the bench to sit for another 1-4 hours until it has bulked out by 50%.
Line a banneton basket (or other bowl) with a towel and flour it well.
Tip your dough out carefully on a floured work surface and gently form it into a rectangle. Take care at this shaping stage to not squash the dough too much and lose all the gases that have been forming.
Watch the short video above on shaping to see how to shape as written instructions are very hard to decipher. I have tried to explain them here:
Take the bottom third of the dough and fold it up so it meets the middle. Take the right bottom side of the dough and fold it to meet the middle. Then take the left bottom side of the dough and fold it to meet the middle. Then take the top third of the dough and bring it down to meet the bottom. Now you have a sort of ball shape. Now you can stitch it grabbing a little bit of dough from the top left and a little from the top right and bring them together to meet in the middle. Carry on doing this down the length of the dough. When you get the bottom, grab a flap of dough and carry it up over top of the stitched dough to meet at the top. This will again create a sort of ball. Now gently grab this ball and roll it gently towards you on the bench. This will create some surface tension. All the while, take care not to de-gas your dough too much. Place in the floured bowel or basket, smooth side down.
Cover with a clean towel and refrigerator for 8-20 hours.
On baking day, heat the oven and a lodge cast iron combo cooker or similar dutch oven to 230 degrees Celsius (446 F)
Flour the bottom of the pot well. (If your dutch oven has high sides, use a long sheet of baking paper instead to lift the dough in and out of withour burning yourself.) Flip the dough carefully out of the basket and brush it with some water. Sprinkle over the oats.
Score the dough using a razor blade or very sharp knife.
Bake in the pot covered with the lid for 18-20 minutes. Remove the lid and bake uncovered for 15-20 minutes more depending on your preference.
Let the sourdough cool before slicing.