I am not sure if this will be of use to anyone else but, I made a right-angle gluing bracket. These can help hold a couple pieces at 90 degrees while the glue dries. The corner is cut off to keep it out of the gluing area. Flat surfaces and a circular cut-out provide places to attach clamps. I used (silicon) rubber bands in place of clamps in the picture. Each of my brackets is two layers of 1/4” Thick Draftboard, stuck together with a ridiculously sloppy glue job.
Right-Angle_Clamping_Bracket-2x.svg.zip (780 Bytes)