I still have one from the stone age, stone simple.
A 5/8" steel pipe rectangle about 20" wide by about 10" high, with a handle about 3 feet long welded to one corner. AT REST, the rectangle should be leaning over about 20 degrees, toward the handle.
You set the rectangle under the bike, sort of laying down, with the handle straight up, then as you lower the handle, one of the long sides of the rectangle makes contact with the lower frame rails of the bike. Adding pressure to the handle lifts the bike, till the rectangle just goes over center and the handle rests on the floor with a bit of pressure from the weight of the bike.
The trick is to get that "golden solution" rectangle height that can accommodate several bikes in your collection! Mine is pretty good, except on the few bikes whose sump sticks below the frame rails.
If you are going to MAKE one, the simple measurement is the height of the frame rails above the ground when the bike is standing still with someone holding it up. You want the rectangle to be about 2 to 2-1/2" taller than THAT measurement. That way, when the stand is fully deployed with gravitational force holding the handle down, you have sufficient gap below the rear tire to easily remove and re-install the rear wheel.
In a perfect world, you could position the stand to lift the FRONT end of the bike just as easily. NOT that I have done this, and NOT that it CAN be done, mind. In fact, I think with a Commando, it would be at risk of rolling backward and FALLING OFF!