Cutting holes with the holesaw is simple enough. As long as there is a guide hole in the middle it will be fine.

Failing that, cut some other material, either wood or metal, say 5-10mm thick and drill a hole in this. Then set it on top, ideally bolt it to somehow and use this as the guide instead of a central drill hole.

Or drill lots of small holes around the perimeter and grind/file smooth after.

Or plasma cutter.

Swaging can look better and it can add strength to an otherwise flat panel. Yes you would need some sort of die setup to create the swage.