Add the water and leaven into the bowl and stir until the leaven is dispersed. Add the 1,000 grams (4 cups) of flour to the mixture and mix thoroughly until you don't see any bits of dry flour. Let rest for 30 minutes.
Add 20 grams of salt (1 tbsp) and 50g (2 1/2 tablespoons) of warm water. incorporate the salt while squeezing your gingers into the dough. Fold the dough until itself after salt is dispersed and place it into a clear container.
Now for bulk ferment/ rise for 4 hours. During the first 2 hours. Wet one hand and pull the corner of the dough up about 6 inches and gently fold over itself. Do it to each corner up to 3 folds every half hour. So a total of 4 turns within that 2 hours. During each turn add the prunes slowly so they fold in gently.
Let rest the additional two hours.
Remove out of the bowl with a wet spatula. Use as little flour as possible and a bench knife to fold and form the dough into a loaf shape. This builds tension and helps with the oven spring.
Once shaped let rest on the bench for 30 minutes.
Flip and lightly add flour then form a loaf.
Mix 50/50 rice flour and wheat flour and coat a towel inside a bowl and place the smooth side down into the floured towel in the bowl.
Let rest and rise for 4 hours or refrigerate overnight.
Heat oven to 500F (260C). Place your dutch oven/ cast iron pot into the oven and let heat up 10-15 minutes.
Remove your loaf from the bowl into the cooking vessel. Score with a bread lame. Reduce oven temp to 450F (235C) and bake for 20 minutes with the lid on.
Remove the lid and bake another 20 minutes or until the crust caramelizes.
Let cool 2+ hours before slicing.