This is based on the archive and article at hackerthemes.com: How to build your own Bootstrap themes.
This repo contains a dockerized version of the original archive, which was necessary to eliminate node version compatibility issues.
Clone this repository, then build and run the docker image:
docker build . -t theme-builder
docker run --rm -v `pwd`:/opt theme-builder
Customize boostrap by editing the files in scss. Preview your changes by opening index.html (as a local file reference) in your browser.