Saw a few versions of this idea and decided I would make a simpler version. I saw some designs that included an elaborate coiling under shelf but that seemed unnecessary. I first thought about cutting cord and adding new plug to make the cord about three inches long but decided for usefulness I would just use a rubber band for the cable. My first thought was to have indentation for the charger base but I am also including a simple design with flat surface.

The flat surface design is easier to print. I would suggest printing upside down. My slicer suggested printing on the side but required a large effort removing the all the additional support material. Printing upside down made for much easier support material removal.

The first file is 6mm thick(with slot) and the second is 5mm (without slot). I did this to make it easier for the short screws to connect better. Additionally, the 6mm (slotted) version was saved in STEP format and the 5mm (no slot) version is an stl file.

I think 15% fill is sufficient but since it is a small print a higher percentage fill will make it stronger.