It's not easy to show it directly especially with the phone itself
. As I wrote, the back is raised about 1mm only. However, I can show this bump indirectly, placing the phone on a desk, putting one finger on the edge by the SOS button, another on the opposite edge and push them alternately while recording a movie with the front camera. The ceiling moves as the phone swings: https://youtu.be/W0aVaKEXwzs
When the phone was new it used to lay stable on the table.
The location is Poland, Central Europe.