How to do it:
What you need:
-The box your filament came in
-A rod (pencils, steel rods, cardboard tube, whatever)
1) Start by cutting the top of the box off and then about halfway down the box on one side (like in the photos). You're gonna need the top open to fit the spool in and the front to let the filament go through. You can be creative and add a brush or sponge to clean the filament as it passes through, but I didn't.
2) You're gonna need some slots on the side to fit a rod to hold up the spool.
A couple of inches down the box should work fine. Just don't cut down so low to have the bottom of the spool touch the bottom of the box. Less friction = better.
So you can use any sort of rod to hold the spool. I used a steel smooth rod that came out of a printer because it was the first thing that I could get my hands on (I had a box of salvaged parts next to me) Anything long and wide enough should work though, perhaps a pencil, cardboard tube, PVC tubing, conduit...
So that's all folks. Easy to make spool holder. When you're done using the filament, just take the rod out and keep it in the box.
Feel free to take this idea and put your own spin (haha) to it and share it with us!