Got some of these Ezy Storage 18L waterproof boxes from Home Depot. They are perfectly sized to hold 5 spools of filament. I dump a bunch of dessicant beads on the bottom, but I didn't like how the spools flop around in there.

So I made a foot thing that can go inside and hold a couple of ½" wood dowel rods for the filament spools to sit on.

Instructions:

1. Press the rod holder into the foot. I used a pair of Knipex pliers wrenches to press them in. It's a decently tight press fit. You can file it down a bit if you want it to be a slip fit. Third hole from each side is where I designed them to be to fit Bambu & normal spools, but you can adjust if you want.
2. Cut two ½" dowel rods to 12.5" length. There is a bit extra space with 12.5", so you could go up to 12.75", but I find that the sides of filament don't have enough space to fall into the gap.
3. Insert the dowels into the rod holders with feet attached.
4. Dry fit the whole thing into the box to get the spacing from the side of box to where the feet sit in the pockets.
5. Place some double sided tape (I used 3M VHB) into the feet pockets.
6. Press the assembled rods/holders/feet into the pockets and press down.
7. ???
8. Profit.

Notes:

• Designed to print with flat face on rod holder down, and the top face of the feet down, so that the feet are pointing up. Feet print fine with no brim, but I had one print out of a few fail on the rod holders when I didn't brim them.
• I was originally wanting to superglue the feet into the pockets, but it turns out superglue doesn't work on the polypropylene the box is made of, so I ended up using VHB double sided tape and that works great. But the feet are designed to sit flush inside those pockets with the arms flush to the bottom of the box.
• I was originally trying to design the rod holders so they'd be a fancy snap fit into the holes to be adjustable, but the small size and brittle PLA made it not work well. I could probably spend hours finding what kinds of clearances and tolerances are needed, but I ended up just going with a press fit. I don't anticipate needing to move them.
• Currently I just dump some dessicant beads in the bottom, but I'll probably make a holder/box for them at some point later that can also hold the hygrometer.