It is time consuming to learn and set up Drupal 8 Bootstrap 3 less subtheme every time when I need it. I decided to create automatic script using my own workflow.
Node.js Grunt.js
themes/contrib/boostrap
themes/custom/willGenerateYourTheme
It make a copy from less version of Bootstrap 3 starterkit and configure it using your values and will set up npm packages.
Make sure you have following folder structure:
themes/contrib/boostrap
themes/custom/
Go to Drupal theme folder using terminal window and download shell file.
run command: sh bootstrap_subtheme_gen.sh
###Gruntfile.js config It has shell support built in and you sould define your drush/drupal executable path or make sure the command works.. If it doesn't suite for your workflow you can just remove shell option.
grunt watch - normal watch command with default tasks clear cache included
grunt watch_all - watches for all the changes and builds the files and clears the caches
grunt watch_twig - watches twig file changes clears the caches