It's best to keep the camera of the device you are using for your interview at eye level. This is so that when you look at the camera, it will look like you are looking directly at the interviewer. If the camera is part of your laptop and your laptop is on your desk, the camera is not going to be at eye level. As an interviewer, I have had candidates position the camera so we were not seeing all of their face, or so that we were looking up at their face from below and nearly able to see up their noses! I put my laptop on top of a box or some books when doing an online interview to make sure that the camera is at my eye level - or I have found raising it up another inch or two (3-5cm) can give me the best angle (and make sure there's no double chin!). Same advice applies to phones or tablets.
My interview tips are based on my years of interviewing experience and my years of interview coaching. I hold qualifications in HR and Business Psychology.