Going wireless will always add a layer of energy loss, in this case heat, during charging, no matter if it is properly aligned with magnets or not. So first step to reducing heat is to charge wired only.

Fast charging is also a way of generating more heat while charging, so limiting the charge speed is also a way to reduce that. If you’re going to charge your phone through the night, it’s probably a good idea to use a 5W brick to manually limit the charge speed. A quick way to enforce that is to use the USB-A port on the brick instead of the C port, that way the PD standard won’t be activated and will charge at a slower rate. (Though if your phone fast charges through USB-A like Quick Charge or SuperVOOC, it will not default to 5W. Use a cheapo brick or a computer USB-A port instead.)

Last would be to limit the charge level to 80%. Batteries are the most stable at half charge and stressed at both extremes, but that’s not practical for anyone to limit their devices between 40~60% charge, so 20~80% is a better compromise. iPhones now have the ability to limit their charge to 80% or 90% in iOS 18, so set that if you can. On Android, you’ll need to see if your phone and OS supports it.