Here is the one I have used with great success. Once stared it’s easy to keep and maintain and makes amazing bread.
https://breadtopia.com/make-your-own-sourdough-starter/
If your wanting a wealth of info on all things bread this is my go to site.
http://www.thefreshloaf.com/
I do Keto and no longer make bread, and did toss my sourdough starter a while back, but may have to get back into it, if only to share with my neighbors.