Use Static HTML Certain URL Path

How to use static HTML for certain URL Path?

So currently i have a website that use NextJS + Custom Router by Express JS served by Google App Engine.

I'd like to use static HTML to create blog for my site in this URL Path (/blog)

I'd like to upload my static HTML Page for my blog into my Google Cloud Storage and then redirect for path /blog to go to the HTML Page. Should i set it up from the express JS Router or can i set it up on higher level?

I only use express JS Router at this moment, no nginx setup.

How can i do this?