[JimDabell]

What are you referring to when you say “flex grid”? There’s no such thing as “flex grid” in CSS. There’s flexbox, and there’s grid. These are two separate things.

I’m not sure what you mean by “resorting to CSS modifications” – surely that’s a given, considering we’re talking about writing CSS?

You don’t need nested containers to do the equivalent of rowspan / colspan with grid. It’s pretty fundamental to the entire feature. You can tell the browser where an element begins and where it ends with grid-column and grid-row. That doesn’t have to be a single grid cell, it can be many – it can span across multiple rows or columns.