In college we were taught that a plinth should be one of two things. Either it's invisible or it's part of the sculpture. Making a plinth invisible is easy; it has to be flawlessly made and painted white. Any deviation from this will distract the viewer.
It's a long time since I made a plinth but, to me, portfolio sites should follow the same principles. They should either be invisible or part of your work. When you're deciding which route to take ask your self one question: Am I a web designer?
Option 1 – Yes I am
If you are, then really it's a no-brainer—you should want to make your own. If you're applying for a web design position, communicating your love of web design is your highest priority. Your portfolio should be an opportunity to demonstrate this love without constraint. Take the time to build something that shows your abilities whether they're coding, design or animation. Don't go too mad though. If it's hard to navigate you'll quickly piss prospective employers off. Once you're proud of it, place a small sig at the bottom to let people know. There's no point going to that effort without getting the credit.
Option 2 – No I'm not
If your abilities lie elsewhere (such as research, testing, prototyping), then you should consider the invisible route. Choose a simple, minimal theme that allows the work to be seen without interference. The goal is to have a site that takes a back seat to the work your presenting. Consider using templates from Squarespace or Behance. There's no shame in admitting you don't have capacity or the requisite skills to produce a whole site from scratch.
Most importantly: BE HONEST. If you're using templates then don't hide it. Leave the logo or watermark on the site. Nothing rings more alarm bells than a website that looks ten times better than the work it's showcasing. Trust me, we always look!