I previously made a dock for my Sony Xperia XZ1 in the same way.
(https://www.thingiverse.com/thing:3021838)

So I made one for my OnePlus 7Pro.
This dock fits with the phone and the clear case that comes with the phone.

Video:
https://www.reddit.com/r/functionalprint/comments/fqz8am/onehandedchargingdockforoneplus7procan\_use/

You attach it to a table or any lip up to 44mm thick.
Sandwich the USB C cable between the two halves.
Install the heat-set inserts into the Front piece.
Screw together.
Use the M8 nut and screw to tighten against the table.

I'm working on improvements.

2 x 4mm heatset inserts
2 x M4 x 20mm Screws
1 x M8 Nut
1 x M8 x 40mm