If you are interested in setting up a website similar to The Stacks project or Kerodon, you can do this using the same framework that powers these websites: Gerby. Unfortunately, until now the instructions to use this were pretty annoyingly only available for the Stacks project, so setting things up correctly was painful and very specific.
We have now created a minimal working example which lists the relevant steps to set up Gerby for a minimal Hello world project. Doing this you'll get an instance of the Gerby with the Stacks project layout, containing just a few tags. This repository is basically a Travis script which performs all the steps required for the installation of plasTeX and Gerby, and then goes through what should be the usual update process for an actual instance.
As usual in any programming tutorial, to go from Hello world to something meaningful is still non-trivial, but at least the first step is now documented. Let me know if you run into any issues!
Caveat Using Gerby for your own project still requires some customisation in the layout, as this is written specifically for the Stacks project.