I have several old unused domains which currently redirect to my website. It occurred to me that rather than having them redirect, I could make web pages for each one with links to my website, and can even include a list of links pointing to specific pages on the site. Thus I would have backlinks to my site.
Will Google penalize me for doing this?
Google will detect pointless links and could penalize you. The sites have to have a genuine purpose. Even if Goggle doesn't detect it now, it may in the future.
In the long run, 2 or 3 extra links are nothing. Any more than that would be obvious to anyone, even a robot, especially since they will have the same ipaddress.
How much traffic does your old domains even get? If they have low DA or traffic as well, then even if there's no penalty, it won't help. Like the other answer said, you should not just insert a link onto a webpage and call it good. That's like purchasing those fiverr packages where the backlink is just posted on a spammy directory.
Backlinks should be naturally incorporated in text. You can write a post on your old websites, if the topic is relevant to both. But if your old sites have no traffic, then you're better off doing guest posts and backlink outreach.
