I designed this tray for a friend; he needed to put the laptop chargers under the desk and have a hole to pass the cables through. He stuck it with double-sided tape so as not to drill into the desk, and it works perfectly.
What I did was reinforce the joints because the weight tended to make it deform a bit, but after more than a year of use, it still looks like the design you see in the actual photos.

There are two STL files, each tray is 20 cm long, and they are mirrored so that each hole ends up at the opposite end if you want to join the two parts and have a tray 40 cm long in total.