This isn’t something I have needed so far, but I probably will in the future. So just to clarify:
When using the hotspot of your phone, does the phone need to be connected to its data or the internet? Or can we use the hotspot directly, without any outside network?
I’m not sure about android but for iPhones you do need to have a network connection with data or else the personal hotspot won’t be active,
But you can use the ppm’s built in hotspot as described by @Adesculpture, it can be turned on in the hidden menu, this doesn’t require data
The PPM can create it’s own hotspot, you can find it in the hidden settings. Then you can connect your iPhone to that hotspot and mirror you iPhone to the PPM.