Ability to create a 404 page in root directory

I’m using Storyblok with Jekyll and Netlify. I would like to create a page in the root directory “/404.html”, which will then act as my 404 page for any pages which cannot be found. I’ve tried creating an actual story within Storyblok, and using the path/slug fields etc., as well as creating a custom page from within the Ruby plugin, however both end up giving me “/404/index.html”, which isn’t what I’m after.

Is there a way to specify that I want a page to be created within the root directory?