How to create and populate the assets folder

[frankhenry]

A few weeks ago I used drupal-bootstrap-styles in creating a D8 subtheme and all worked fine with a couple of small exceptions. Yesterday I came back to it with a view to documenting the process but now the build process, i.e.

yarn build

followed by

yarn install

fails with this error message:

[email protected]
  Bootstrap.install bootstrap (456μs)
  Bootstrap.getPath bootstrap (463μs)
  fatal ReferenceError: name is not defined
    at Bootstrap.getPath [as getPathAsync] (/projects/drupal-bootstrap-styles/lib/Bootstrap.js:107:21)
    at LoggerTask.run (/projects/drupal-bootstrap-styles/lib/Logger/LoggerTask.js:52:36)
    at queue.add (/projects/drupal-bootstrap-styles/lib/Logger/Logger.js:296:111)
    at run (/projects/drupal-bootstrap-styles/node_modules/p-queue/index.js:205:22)
    at PQueue._tryToStartAnother (/projects/drupal-bootstrap-styles/node_modules/p-queue/index.js:167:25)
    at Promise (/projects/drupal-bootstrap-styles/node_modules/p-queue/index.js:222:9)
    at Promise._execute (/projects/drupal-bootstrap-styles/node_modules/bluebird/js/release/debuggability.js:313:9)
    at Promise._resolveFromExecutor (/projects/drupal-bootstrap-styles/node_modules/bluebird/js/release/promise.js:488:18)
    at new Promise (/projects/drupal-bootstrap-styles/node_modules/bluebird/js/release/promise.js:79:10)
    at PQueue.add (/projects/drupal-bootstrap-styles/node_modules/p-queue/index.js:199:10)
    at Bootstrap.args [as getPath] (/projects/drupal-bootstrap-styles/lib/Logger/Logger.js:296:36)
    at Bootstrap.install [as installAsync] (/projects/drupal-bootstrap-styles/lib/Bootstrap.js:140:27)
    at LoggerTask.run (/projects/drupal-bootstrap-styles/lib/Logger/LoggerTask.js:52:36)
    at queue.add (/projects/drupal-bootstrap-styles/lib/Logger/Logger.js:296:111)
    at run (/projects/drupal-bootstrap-styles/node_modules/p-queue/index.js:205:22)
    at PQueue._tryToStartAnother (/projects/drupal-bootstrap-styles/node_modules/p-queue/index.js:167:25)

Total time:	716ms

It's failing because there is no assets folder present. When I copy the assets folder from where I successfully compiled the styles last time, everything works as expected. The folder looks like this:

The trouble is, I wasn't paying attention to where the assets folder came from so I don't remember if the build process created it or if I copied it from somewhere. Either way, I can't replicate it. I've cleared all node and yarn caches, even tried it on a new vm. Can you help? Thanks!