+ It is very easy and quick to make. It takes less than 5 minutes to make it.
+ The mounting/unmounting is very quick
+ When unmounted it fits your pocket.
+ You will need only white cardboard, foil (e.g. from chocolate), and adhesive tape.
Scissors, pencil. For more accurate result cutting knife is also desirable.
Cut a rectangle of cardboard which has about 12cm width and about 15cm height. Exact dimensions are not critical.