Bolt/screw base for phone mount

I needed a base plate to bolt down a phone mount to a boat. This fits my Ibra mount:
https://www.amazon.co.uk/Windscreen-Suction-Degrees-Rotation-Samsung/dp/B008MM9FEA

The larger square is an insert from the original Ibra mount with a knurled washer to stop the mount arm moving.

UPDATE: replaced with V2 model with stronger bracket.