The proportions are variable but I use 100% flour, 75% water, 2% salt and 15% sourdough leaven. I've used various proportions of 100% stoneground flour, but often use a combination of your stoneground hard red, AP hard read and regular all-purpose white or sometimes einkorn or dark rye.
For my method, I pre-mix the flour/water/salt early in the morning when I wake up and mix the leaven at the same time. By the time I get home after work, the gluten will be well-developed and the sourdough will be ready to mix. I mix and fold the leaven into the dough. 3 times every 10 minutes. Then I'll fold the dough every 30 minutes for 3 hours then let it rise on its own for another 30-60 minutes. It's usually risen by 30-50% by four hours. Then I'll remove it from the container and pre-shape 2 rounds. I'll let it sit for 30-60 minutes depending on how active it's. Then I'll shape it into a batard shape and put it in a proofing basket and to the fridge for the night. After 12 hours or so it's usually ready to put in the oven. I heat the oven to 500F for an hour with a dutch oven inside. I'll bake the bread for 20 minutes with the lid on at 475F, then 12 minutes at 425F then 400F for the rest.