I know there's a lot of different sourdough start recipes out there, all I've ever done for 35 years is, 2 cups of flour, 2 cups of warm water, 1 heaping tbl spoon of SAF yeast & a tsp of sugar. I cover it & let it set for at least 24 hours, longer is better.
My kids & grandkids ate SD pan cakes, SD bread, etc from this recipe for all those years & never knew the difference from a "good" recipe.

Dick