Warm water in microwave for 1 minute on high. Weigh flour and place in large bowl. Mix starter and 350 mls water thoroughly in another bowl. Pour mixture over flour and mix until all flour is folded in. Let dough rest for 30 minutes. Work salt and remaining water into the dough by squeezing and mixing by hand. Transfer to a smaller container, cover, and let sit for 30 minutes. Turn the dough by stretching and folding over 3 or 4 times. Repeat every 30 min for 3 more turns (book recommends 5 more, but 3 is usually enough). Let dough rise for around 4 hours.