Una Kravets shows how to make layouts in CSS Grid with flexbox fallbacks for browsers that don’t support those grid properties just yet. Una writes:
CSS grid is AMAZING! However, if you need to support users of IE11 and below, or Edge 15 and below, grid won't really work as you expect...This site is a solution for you so you can start to progressively enhance without fear!
The site is a provides examples using common layouts and component patterns, including code snippets. For example: