This is a support / mount to hold onto a power brick for an electronic device. My initial need was to get this off the floor and mount it to the bottom of a sitting chair, but this could easily be adjust for a desk or other purposes.

My power brick was approximately 50x120x33 mm, but these come in many different sizes. Luckily, I created this in OpenSCAD and you can use customizer to change the base dimensions and other variables. The screw cut outs are 4mm by default with a bit of an inset of the screw head, but you may want a thicker base to full countersink it. There are other elements you can modify to meet your needs.

Warning/Disclaimer: Be sure that you are properly ventilating your power brick as it could get hot. Ensure you use an appropriate material for printing which can withstand the heat. No warranties implied or explicitly noted per the license.