django-bootstrap-static | Bootstrap static content wrapped in a pip | Frontend Framework library

Let's start by taking a look at how Django's STATICFILES_FINDERS works:

The default will find files stored in the STATICFILES_DIRS setting (using django.contrib.staticfiles.finders.FileSystemFinder) and in a static subdirectory of each app (using django.contrib.staticfiles.finders.AppDirectoriesFinder). If multiple files with the same name are present, the first file that is found will be used.

Note the line that it searches the static subdirectory of each app.

Now let's take a look at the folder structure of django-bootstrap-static, we see two main folders bootstrap and fontawesome. And if you look inside, they only contain __init__.py and a folder named static.

Basically, both bootstrap and fontawesome can be seen as Django apps (i.e. similar to apps you create with python manage.py startapp). By including bootstrap and fontawesome into your INSTALLED_APPS, you've included them as apps in your own Django project and Django's STATICFILES_FINDERS will look into these two apps too to look for folders named static. So in this case it's able to find these static files and include it when you run python manage.py collectstatic.

EDIT

I forgot to answer the part about SASS. To do so, I would probably use a library like django-sass-processor and also create my own app called bootstrap using the python manage.py startapp bootstrap and create a folder called static inside. Within the static folder I would create my SASS folder structure and do my necessary overrides and personalisations.

Bonus: A nice way to architecture your SASS project can be found here