I liked freecad actually. Once I figured how to use it, it was so much easier to make your own creations than in tinkercad. I also felt like I got better with it quick, and definitely feel like I’m a step up from where I was before.
First the basic tutorial:
Below are the clip I made for my charger and a pictures of where it would go on my desk.
This is the clip, with a 4mm crevice with a little pocket inside to hold the cable snugly. The big hole is 30X30mm, made to just fit on a protruding part of my desk. 
Circled is the protruding part of my desk on which the clip would fit.
Lastly I made two simple blocks that would hook on to each other.
Block A 
And Block B, made to slide into block A.
Looney 