There are many adapters for the DJI Mavic Pro's handheld R/C Controller to attach a tablet. Almost all of them have a complicated ballhead or hinge mechanism attached to a vice that holds the tablet into place.
This adapter is easy to make, and packs in a fairly low profile to make it easy to pack along with your Fly More kit, whether in a small bag or a hardshell case. No more unscrewing, no more sagging hinges, no more lost pins or bolts or parts. Also, it is easy to protect the tablet screen between flights if you like to use the magnetic flap screen covers.
A wide variety of cheap tablet cases exists already for each tablet on the market... so why not leverage that? They're often cheaper than the vice adapters by a wide margin. Print this adapter, schmear some two-part epoxy or other strong adhesive onto it, and boom, you are ready to affix the controller to the tablet.
Two things to watch out for in ANY DJI Mavic Pro Controller apparatus. Make sure that you assemble it in such a way that the controller's sticks are not impeded in any way (including fitting your hands to reach the sticks). And if there are any magnets involved in the parts, such as a magnetic "screen off" feature, they should never get close enough to the sticks to interfere; the DJI controller will display "STICK EMI 1" if there is any electro-magnetic interference detected with strong magnets near the controller's sticks.
half your nozzle diameter
With a strong inexpensive two-part epoxy, this becomes a permanent attachment to your own third-party flat tablet case. You want to print for strength and solidity, so don't skimp on the infill. The layer resolution is not critical, but around half your nozzle diameter will give a quicker print without sacrificing strength. I like PETG for utilitarian brute parts like this, but this part requires no flex so feel free to print with any material you can avoid significant baseplate peeling.