Just 1It also depends upon how many pieces you're making. One? A thousand? 43 million?
This is what I'm leaning towards right nowDrill holes at each corner, then an angle grinder with cutoff wheel, or a jigsaw with a metal cutting blade to connect the holes. Go slowly with the jig saw. Clean it all up with a file.
Best tool for the job is a Dremel with a cut off wheel the smaller the better. Cut from the back side and put masking tape on the front side.
I cut through the tape in this instance. Normally you use the tape as a cut guide in this case it prevents the sparks of the cutting wheel from defacing the stainless steel.