This was a project I designed in Inkscape live at Decatur Makers, a family friendly makerspace in Atlanta, GA. There are many other ways to design for the laser, many of which are probably better, but this worked out ok. It's also a decent alternative for those who haven't taken the leap to some form of CAD. The video is below.
This spool holder is designed to work with most typically-sized 1kg filament spools. It was designed for use with .202" thick plywood, which is roughly the size of 1/4" plywood from the big home stores (don't get me started on that). I suspect it'll work fine if you're a few thou on either side of that thickness. The file I've provided is not adjusted for the kerf of any laser, so the tabs will certainly fit, but it'll likely be sloppy without glue.
The cross pieces can pretty easily be lengthened to accommodate a thicker spool. A wider (diameter) spool will be harder to accommodate. You'll need to grab the top nodes of the side pieces and move them up.
The design video probably isn't for the CAD nerds out there and I would probably do some things differently next time (like use a color that is actually visible towards the middle of the video), but hopefully it will help someone out.