Do you like this patent for full-screen mobile phone? It is similar to an off-screen camera, but the self-timer effect is ten years better than that of an off-screen camera.

Your method looks really good, but the camera should be small, so that it can be hidden under the numbers and not easily seen by others, otherwise the time display will be ugly if it is too large. In any case, in the future, when the technology of off-screen camera becomes more and more mature, the effect will definitely be the best.