My work desk is flat. But yes, it does not grip the phone since it was probably made for generic Qi charging. I can't knock my work desk as it is against the wall

An application of velcro will probably help matters, although I'm leaving it on my backburner for now on how to integrate the charger with some kind of stand or holder. The TS of Nexus 4 thread mounted it in his spiderpodium holder so he can charge the N4 without slipping.

There is one guy on the XDA N4 forums who mounted it into his dashboard, and he added magnets to it as well. I can make those holes but I don't think we can get those magnets locally.