Seen something similar to this on Amazon, this is sized to slide onto my desk, which is about 16.5mm thick, so no screw is needed to secure it to the desk, just friction fit. 

Cup holder is sized to be able to fit a 40oz Stanley tumbler. 

Very new to using Fusion 360 so it is a bit rough around the edges, there probably is a lot I could have done better. 

The cup holder is attached with a tongue and groove joint, so will be able to design other accessories for it, thinking next one will be a controller holder. 

Printed on my Neptune 3 Pro, set to 50% infill and used supports, probably could get away with less infill, but didn't want to lose any strength. Just printed in PLA. 

As this is my first proper model, I welcome any suggestions for any improvements, and I will be tweaking and changing it too once I start using it every day, so any changes to the model will also be uploaded here. 

Feel free to remix.