Adding rear corner to a corner cabinet

Ok, so I put myself in a bit of a pickle and am trying to find a way to best remedy it. Doing a kitchen remodel and I forgot that the lazy susan corner cabinet I got doesn't come to a complete corner in the back, but rather angled off.

The goal was to have a peninsula with this cabinet in the corner and then on the back side, having some decorative panels. The problem is that since the back is missing the corner, I have nothing to attach the panels to on the back side.
For reference, my corner cabinet looks like this:
https://www.renovohome.com/product/l...steel-baskets/

There is one stud on the wall in that empty space and tile floor that I might have to drill into, but I'm not sure how to best frame the corner up.

Perhaps just a 2x4 running down the wall to be flush with the rear face of the cabinet and anchored with sheetrock anchors?
Ideas?
Thanks!

 

I usually use 1 x 3 poplar or 1 x 4 pine SFS, any wood strips will do.
Your idea is good. A strip on the wall using anchors or adhesive and brad nails, a strip at the floor, and a strip at the top.

I cut the top and bottom strips at a 45° angle where they meet the cabinet and screw them into the cabinet back and then secure them to the wall strip with L brackets or whatever is handy.

You also want a short cleat screwed to the wall at the top to support the back corner of the counter top.