I am new at sourdough baking although I have made a few loaves, one whigh was the first one with this new starter came out fairly well. The starter is from the Oregon Trnail strand which you can get for free for just sending a self addressed stamped envelope or a dollar donation. I had no problem getting the starter to bubble or to rise a nice sponge. But after adding the flour and letting it rise it does not have enough structure. My recipe is 1 cup starter, 1 cup water, mix to combine, 2 cups flour for the sponge. After the sponge has doubled (about 8 to 10 hours) I add 1/2 cup water and 2 1/2 cups flour, 1 1/2 tablespoons salt shape the dough into a ball after stretch kneading a few times. Then let it rise in a cast iron pan. This is where it tends to spread out and not up enough. I use a cast iron Dutch oven to bake for half an hour then remove cover to brown about 15 minutes. I really would like to bake the bread on the cooking stone I have. Pizza pie stone. But I fear the bread will flatten out even more as ther are no side walls. Can anyone help me with this. Or maybe I need a more active starter. I bake at 450 degrees 30 minutes.