My printer sits in the basement, which sits at a fairly constant 18-20deg and 60% humidity. I was having issues keeping my filament dry, but after trawling the internet couldn’t find a single solution that i really liked, so i remixed from a few sources.

I now have two fully kitted out Dry Boxes with triple spool holders, and one without the spool holders for bulk storage of open spools.

The initial dimensions of the spool holders were not quite wide enough for some of the spools of filament i had, so i modified the design so i now have 1x wide and two slightly narrower spool holders per box.

To connect the spool holders i used 12mm M3 socket head bolts.
The design of the legs is not ideal, but it does the job and keeps the filament up out of the silica gel.

The bulkhead penetrations i used are linked below. I needed angled penetrations because my filament sits on top of my print enclosure.

To get a nice seal i used some self-adhesive glass sealing strips from the local hardware store.

This box won’t actually dry wet filament out, but it keeps dry filament dry. Using a decent amount of silica gel my dryboxes have been held constant at 10% humidity.

Components:
Ikea 22L Samla plastic storage box
Rubber self-adhesive glass seal

Angled Dry Box Filament Guide: https://www.thingiverse.com/thing:2896547

Dry Box Humidity Sensor Mount: https://www.prusaprinters.org/prints/34461-drybox-humidity-sensor-mount

Lid Fasteners: https://www.prusaprinters.org/prints/14568-ikea-samla-22l-lid-fastener

Spool Holder Inspired by: https://www.prusaprinters.org/prints/72870-ikea-samla-filament-spool-roller and https://www.thingiverse.com/thing:4976052

Bearings: 608RS/ZZ bearings i.e. https://www.amazon.de/-/en/gp/product/B08F2HGQN7/ref=ppx_yo_dt_b_asin_image_o03_s03?ie=UTF8&psc=1