I just did my first test using a stencil for plasmacutting.
-I did the design with CAD (unfolding the surface I needed
-gave the outline a 3.5mm offset
-cut it of corrugated cardboard
-used double sided tape to fix it on the sheet-metal (only a few spots)
-used the plasmacutter (if you are to test that: always try to pull the nozzle of the cutter, pushing doesn’t work well)
-bend it and weld the seam (I know! Has been about 1.5 years I used my tig welder. Out of practice.
I have to work a bit with the offset amount and need a bit more practice with the cutter, but basicly it works well enough.
(compressor and plasmacutter are about 450,- these days. small ones for up to about 5mm metal)