The strategy here is to transpile the stylesheet file to a css-in-js file so that it can be loaded and hot reloaded both on the server and the client. For this purpose I created a babel loader plugin called [babel-loader-wrap-in-js](https://github.com/davibe/babel-plugin-wrap-in-js).
Another babel plugin [module-resolver](https://github.com/tleunen/babel-plugin-module-resolver) enables us to import stylesheets from js (e.g. pages or components) through a `styles` directory alias rather than relative paths.
The `sass-loader` is configured with `includePaths: ['styles', 'node_modules']` so that your scss can `@import` from those places, again without relative paths, for maximum convenience and ability to use npm-published libraries. Furthermore, `glob` paths are also supported, so one could for example add `'node_modules/@material/*'` to the `includePaths`, which would make [material-components-web](https://github.com/material-components/material-components-web) (if you'd like) even easier to work with.
Furthermore, PostCSS is used to [pre-process](https://blog.madewithenvy.com/webpack-2-postcss-cssnext-fdcd2fd7d0bd#.r6t2d0smy) both `css` and `scss` stylesheets, the latter after Sass pre-processing. This is to illustrate `@import 'normalize.css';` from `node_modules` thanks to `postcss-easy-import`. [Autoprefixer](https://github.com/postcss/autoprefixer) is also added as a "best practice". Consider [cssnext](http://cssnext.io) instead, which includes `autoprefixer` as well as many other CSS spec features.