This is a pretty old project, I just found the pictures and wanted to share it with you. My wife wanted a sideboard for her desk. We still had an old shelf. One friday morning I disassembled it...

What I did was: I turned this...

...into this:

This is how to do it:

The only thing you need for this is an old shelf like this. You can get it at IKEA, it is named Billy. But other manufacturers have it as well. You could even buy wood at the hardware store.

Break down your Billy shelf into basic components.

Assemble them differently.

It is a pretty simple construction.

Make sure it has the same height as your desk.

Leave a little space between desk and sideboard so your drawers can be opened.