The best location to place your BON CHARGE sticker is on the back of your phone or phone case nearest to where the charging port is located.
This will ensure the negative ions produced can interact with the positive ones emitted in large quantities from the bottom of your phone.
It does not matter whether the sticker is on the main phone body or the case as it will work the same in both locations.
If you are placing your BON CHARGE Harmonising Sticker on any other device or electronic, closest to the power source is always recommended.