Rule number one of podficcing: Never create podfic without the fic author's permission!
The best case is when an author has issued a so-called "blanket statement" in their AO3-profile, where they state which kinds of transformative work they generally allow to be made of their fanfiction. If you can't find such a statement, there's no way around writing to them and asking, and no: "The author doesn't respond / check comments / can't reach them / can't find them" are very sad and inconvenient, but are not acceptable reasons to skip getting permission. Consent is key. Never create podfic without permission.
As a service to the fandom, I've started collecting a list of authors who have given permission to create podfics of their works.
If you're an author and would like to be included in the list, please fill out this form. Thank you!
(the list is still being worked on)