This is a simpler method: just have a stand (again, the acrylic stores help a lot) and support it on the desk by putting the camera face down.
If you want to invest a little, there are cameras that already come with support, such as Ipevo:
Pros:
- You shoot the user's fingers and the interaction on the screen.
- The person can pick up the cell phone and move around with it, with some mobility, as long as they do not leave the camera's range of action.
- Because the camera is attached to the computer, you can keep track of what the person is doing (and adjust the camera if necessary).
- If the media is loud, you can use the person's cell phone and also see a bit of the context—sometimes you can shoot a note ...