....Here is what I use...
A general purpose jig. Its a piece of formed galvanized metal I scrounged from work. I use magnets to help hold pieces for gluing. I have a couple of larger speaker magnets (not pictured) that I have used to straighten frames with. If a frame gets warped , I placed the big speaker magnets either on top or either side of the frame and let it sit in the window frame for a day or two or use my wife's hair dryer on it for quicker results. Same thing with the spreader clamps....if I have something that absolutely can not be moved once set in place and that is thick enough as to not be distorted by the clamps , then I can use them.
I have a small assortment of stand alone, base supported holding tools (6" spring clamps, 3rd hand devices) that I have used w/ the jig to build in a vertical verses flat position
If it gets gunked up with glue, resin, etc. etc. I simply scrape it clean.