This design is an original inspired by other designs from Walter (like http://www.thingiverse.com/thing:796504) and Skalla J (like http://www.thingiverse.com/thing:2103466). This is made to fit spools that have an axle ID of 32mm and OD of 60mm.
With this design you have four options for trays which are sized to half the height of a spool. This means a total of 8 trays to fill a spool, pick and mix the ones that best fit your needs!
If you print using infill (rather than solid) make sure you are using a setting like "Expand skin into infills" found in Cura 2.5. This makes sure the walls have no gaps near the floors.
To assemble use the included jig to make the holes in your spool. For the first hole tape the jig in place. For following holes place the bump from the jig in the previous hole. I used a drill press to ensure the holes lined up well. When drilling put something in between the two flanges of the spool, like a book, so they don't flex.
I made four custom pins out of M5 threaded rod but you could use M4, M5, 6/32, or 8/32 bolts that are 55mm long (2" might be short). You could also use plain rod, wood dowels, clothes hanger wire, etc.