I have consistently struggled to apply thin self-adhesive copper foil neatly enough by excluding air bubbles and avoid unsightly creasing, so another approach was required. I carried out a test to see if I could successfully CNC cut a pickguard shield from 0.1 mm thick copper sheet like this from Fred Aldous:
I held down the copper sheet to the CNC machine spoil board using low-tack craft double-sided adhesive tape. This test sheet is only 300 x 215 mm and is not quite wide enough to accommodate the full cut and therefore rides up and creases at the edge in two places. I believe that the cut would have executed perfectly if a wider sheet was used. However, this piece was still salvageable and able to be glued to the back of the pickguard. Fred Aldous also supply a roll which is wider (30 cm) and longer (3.6 metres):
The video is speeded up 8x. I used extremely conservative feeds and speeds: Spindle speed: 600 rpm, XY feed rate: 400 mm/min, Z plunge rate: 30 mm/min, depth per pass (0.1 mm on a single pass only), cutter: Trend solid carbide 90 V-groove. I was satisfied with the outcome considering that it is so easy to crease or tear the foil during cutting or removing it from the spoil board without creasing it. It lifted off nicely with a heat gun. Initially I tried gluing it on with brush on cyanoacrylate superglue but the copper did not fully adhere in places so I bought some strong spray contact adhesive instead.