I have an Ikea Billy shelf for bedside table, which is very convenient, but always crowded with little things that don't like dust, such as ear plugs.

Here is a solution that can easily be resized, a smal drawer that can be mounted underneath a shelf and made lost space usable.

Since I use it for a few light items I just used double sided tape to mount it.

Easy to print, no support needed.

If you don't use the gcode, make sure to print twice the track.stl part: one for each side of the drawer.

It's been so useful so far that I've decided to make a wider modular version, where you can down-stack several drawers.