I'm trying to create a static website. I want to be able to do some simple preprocessing, such as including one page within another, without the use of PHP or JavaScript.
Jekyll seemed perfect for this, especially given its support on GitHub pages.
However, after trying a few themes and trying to tweak them into what I'd like, I found myself fighting the themes which made them more of a hindrance than helpful. As a result, I decided to try and work without them and just use Jekyll as a fancy preprocessor and plugin platform (for things such as jekyll-redirect-from).
Much to my surprise, I couldn't find any information on how to do this, on how and where to place what files to generate a useable site. It feels like this should be incredibly simple to do, but the only route I've found so far is to create my own theme. This seems like overkill to me.
TL;DR
How can I create a Jekyll site without using a theme? Where can I find information on what files I need, where, what needs to be in them and so on?