Suppose, you buy some decent domains with 100-200 RD or more with a clean history and all. It is possible for you to rebuild the site and it loads everything right.
Then you link to one or two of your sites from the homepage and much more from the inner pages that have links or is somewhat relevant to your website. If possible you add a few hundred words to make the page more relevant to your link.
You also have other PBNs that links to your sites, these are not the only way for PBN you…