Can you add the sidebar into a block?

I am creating a new layout and I want the sidebar to show under the featured post, here is a mockup
https://www.screencast.com/t/X2YMWMkFvj

Do you know if there is a way to add the sidebar into a block so it shows? I can't seem to find a way to do it on google.

Or would I be better creating an element of the featured post and add it to the site that way?

Thanks