Host a static site alongside WordPress

I’m attempting to host an old static portfolio site along my WordPress one, but do NOT want the site to be my landing page. I have all the files on the server in a separate folder on root next to the WordPress folder, but when I try to manually navigate to it (example.com/portfolio/index.html) I get a ‘nothing found’ page in my WordPress theme, so it’s obviously trying to locate a page in my WordPress database. Is there any way to do this without making it my front page? I’ll be 100% honest, this is my first time trying to host a page on the web, so Apache is something I’m still learning.