I’m not sure that is the normal method with Sourdough- I’ve been making it for a few years and I’ve spoken to several that have gone on courses and their method seems similar to the one I use.
It employs a ‘starter’ rather than keeping some dough. The starter is sort of self-perpetuating if you feed it regularly (every 1-2 days if not kept in the fridge):
Equal quantities (in my case 150g) of starter, flour and water are mixed together, it’s allowed to ferment for 12-24 hours then 150g of starter is the base for the sourdough mix; the starter certainly isn’t a dough, you can pour it.
Here’s the recipe I use:
To the 150g of starter I add 450g of strong flour, 250g of water and 20g of sugar.
Mix for about 10-15 minutes then add about 12g of salt and mix for 5 minutes or so.
Take it out of the mixing bowl, stretch a bit then form into a ball.
lightly oil the mixing bowl, return the dough into it, cover, then leave to rise until it’s at least doubled (generally overnight).
Take out of mixing bowl, shape into a rectangle, fold a third in, then cover with the other third, turn through 90 degrees shape into a rectangle and fold in again (I do this twice more). Purpose of this is to build layers in the dough.
Then shape into a tight ball (by applying a little pressure on top while pulling it towards one to get it to turn in on itself from underneath, turn through 90 degrees, repeat probably 6-10 times.
Place into a proving basket, cover and depending on how lively the mix was place either in a warm place or the fridge.
Wait until it’s almost doubled in size.
Heat oven to about 230 degrees, with a cast iron casserole in it (maybe with 50% more height than the dough has risen to). Let everything get hot.
Get 8 cubes of ice (actually probably 4, my icemaker makes small cubes)
Put some siliconised baking paper over the dough, turn it out of the basket.
Cut a slightly curved slice using a razor in the top of the dough, running the length about 1-1.5cm deep.
Put the dough in the dutch oven, put ice at either end (under the baking paper). Put the top on fast.
Place in the oven for 25 minutes.
Take the top off after 25 minutes and leave for a further 15 minutes.
Let it cool on a wire cake cooling thing (don’t know what they’re called…)
Anyway… that’s the method I use. White bread easier than brown.
Oh and once I’ve made a dough, I feed the starter again (equal quantities of starter, flour and water). Can be wasteful but the spare starter with a little bicarb can cook into crumpets (but this is always messy so I don’t often do it).