I remixed @russiancatfood's original design (https://www.thingiverse.com/thing:696271) to fit the phone mount on my Hyundai i20.
You'll need all the files (except dash-plug-right, dash-plug-left and lock_clip) from the original design plus my new files.
Screw left and right plug to the hyundai-insert with 2 M3 15mm screws. For this I tapped the M3 thread into the insert beforehand.
Insert the whole mount and secure it with the plug.