Best way to add a sidebar to a Block - Loop Template?

Hi guys -

Just getting my head around how GP does things and am a little confused.
Looking for tips on the best way to create a certain layout.
(Which will also help me understand the relationship of different GP elements, I think).

I'm using the Block Loop Template to create a Blog Archive.
I currently have a two-column Grid inside the GP Query Loop and so far so good.
But I want to add a sidebar to the right of the Query Loop container.

The end goal is just to have a classic two-column post archive with a 3rd column sidebar.

Would it be best to:

1. create this by adding containers on the Block Loop Template (as picture below)? This works to a point... but can I insert a sidebar in the third column using this method?
2. create a Block Loop Template and then separately create a Blog Layout with sidebar, and then assign a Sidebar Element to that layout?

Image: how I've approached it so far. But I think I need to revise since this method doesn't seem to allow me to insert a GP sidebar element (which makes sense since it's an Element, not a block).

Thanks for any advice.