I am surprised they didn't try #5, etching/scoring the sheet with moderately deep cutting-line, using a sharp piece of (most likely) crystalline quartz, then bending. That gives a line of weakness, and makes it easier to bend without distortion of the sheet.
Also, pounding with stones doesn't sound like a very high quality finished sheet. hardwood (or less likely, heavy antler) mallets, with a hide facing, OTOH, takes longer, but gives a better finish.
Personally, I think my first "project" would be to make a copper hammer & anvil!
Same here.
I wonder how long it would take to figure out quenching heated copper would make it more resistant to bending (tempered) versus slow cooled copper (annealed). Even a stone chisel might have been on my list as well.
I must admit I often find it amusing when academics try to sort out tradecraft...