This is a three-part MagSafe mount for any display that is up to 22mm thick. You can either use the rear camera (for example as Continuity Camera) or flip the holder over and use the front camera the additional screen. There are also customizable versions, so you can use (almost) any charger you want. (max. diameter: 58,6mm; max. thickness: 6,5mm)
Put the three parts together. insert the nut at the side and add screw the screw in from the other side.
Depending on how you put in the top part with the magnets, your camera will either be facing forwards or backwards.