Creating non-blog post new pages with blogdown

I'm finding it effortless to create dated blog posts with blogdown but surprisingly difficult to create other forms of content. For example, how could I create multiple pages under the About tab of this demo Hugo Lithium site? I made some progress creating a _index.md file in an about folder under content, but couldn't control the content in that file, presumably since it's determined by a list layout that comes with the Hugo Lithium theme. Do I have to find (or create) a theme with the content structured in the way that I want? My preference would be to have a blank slate that I can control, GitHub Pages style, where I choose what's linked to what, and deal with themes as little as possible: my first impression is that they are overly intricate--and restrictive--for my purposes.