Hi there!

This is a remix of my original design, this remix is scaled up slightly and includes a hole for the screen of a small phone.

I designed it around an Iphone SE, which could fit in there comfortably (140x68x8mm, LxWxH). 

Four 4x16mm screws are needed to hold the underplate.

I also added the fusion360 files so you can edit it to hold other sizes of phones. And u could make a system on the underplate that holds your specific phone so it doesn't fall out.