Use as a basis the recipe from:
1 cup sourdough starter
1 1/2 cups warm water
1 1/2 teaspoons salt
1/2 cup white sugar
1/2 cup corn oil
6 cups bread flour
but added less oil and less sugar. Besides, used a mixture of olive and vegetable oil instead of the corn oil (should I use corn? what are the advantages?) It raised very slowly overnight
(almost none) and I was forced to accelerate it with hit. At some point I thought that I failed.
However, it gave a strong spring ( I used 380 K) and the bread, both boule and baguettes, was great.