So instead of starting with a "rectangle", you would start with a shape more like this, and after you "Shrink and Stretch" it with something like those tools I linked too, it would roll into a rectangle that met up at the edges into a mobius... (This is metal on the table. Not in MoI) I suppose figuring out where the stretch and pinch is, is your point and where you mean you are at. I think the previous video can help with that part along with this demo

There is alot of calculation that would go into being able to do it that way. I would just get it close enough to hit with a hammer. Some young kid may do the calc and do precision work!