Here’s a practical cut I made to create a custom switchplate for a 4" standard metal electrical box. I needed the decora-style opening for the speed controller, and the round hole for the industrial panel switch. I made this in two parts - one being the cover with the engraved lettering, and the second being a standoff so that the panel switch had more clearance as far as depth into the box goes.
Another practical note that I believe has been mentioned here before, the website mcmaster.com, in addition to having all sorts of interesting parts, tools, and materials for sale, also has CAD files for most of the things they sell. So if you want the layout and spacing for an electrical box and various cover options that are available, you can look up the parts, download the CAD files, and import into your vector editing software… saves the hassle of taking lots of measurements.