I would just tend to link to the websites I've built from my homepage. If the client has managed to trash them since switching them live, take a screengrab of the site in the state you handed it over in. I'd also add some general info on the technology used, any challenges you solved in the course of building the site, and how you managed to bring value to the client.
CodePen is cool and all that, but it doesn't really support navigation or anything beyond showcasing a particular technique. That's not to say you can't use it to host sites—you can, I just wouldn't use it to host my portfolio.