Four card feature section built with HTML and CSS

This one seemed to have challenged you a bit man. From what I can sketch, I'm thinking of tackling it in two ways for the bottom containers:

1. Create a flex box container with three row containers in the default arrangement. The middle container will have the two other column arranged flex containers or mix it with grid.
2. Grid item with three repeat row frames and in the middle frame, create another grid container or flex-box it.

That's just how I would tackle it's design.