Corner Clamping Tapered Parts?

Hi there!
I hope this is the correct area to ask, but I'm about to do a bunch of brazing on 0.125 aluminum foot shell parts (about two dozen) for a full size Star Wars R2D2 build.
Problem I'm having is that R2D2's feet / these parts are pyramid shaped and requires a weird corner clamp angle I'm not sure how to achieve.

For instances, the very first parts you put together are corner welds, but tapered out:
https://ibin.co/5i1wGe9SP6Hk.png

Normally I would just square my parts up by eye and let it rip, but because there are so many parts here that need replica precision, I want to get things truly squared up and not just by eye.

How do you normally clamp a 90deg corner that tapers?

Thank you in advanced!

Hi Devin, and WELCOME to a TOP FORUM.
I'd make 2 corner blocks out of 2" X 1/4" flat bar, at the correct angle, one for each side that can be clamped to the Aluminum to hold in the correct position.
Having the flats sitting on a sheet of steel will allow a magnet to hold it all in place.
HTH
Kryn

Welcome to the forum Devin.

Ross