(1) clipboard - I had this laying around
(1) stainless steel door hook - dollar store
(2) 3/4" square dowels - Lowe's
-the bottom slot on the door hook was 3/4" that's why I selected that size dowel
(2) M4-10.7X60 bolts - Lowe's
-these were the widest M4 bolts I could find and a just a mm or 2 wider than 3 widths of the dowel
(3) M4 wing nuts - Lowe's
-I chose these so that the desk would be easily disassembled
(2) #10X1-1/4" wood screws - Lowe's
(4) #10X3/4" wood screws - Lowe's
(1) champagne cork - saved from New Year's celebration
All of these parts were chosen to be as inexpensive as possible (I had the clipboard, the dowels were only about $2.50 each, and I spent about $6 or $7 on hardware with a few bolts and several wood screws left over). Without the M4 hardware you could probably make this cheaper, but I wanted to disassemble this desk and put it under my bed when it wasn't in use.
The pictures and picture captions will take you step by step through how I made it.