I came across a YouPipe video of a guy (James Archer) who made his own color correction chart, similar to a SpydrCheckr 24. I had thought of making one myself so it was kismet.
I sourced the color samples from my LHS (for free!), cut them to size and then used PVA glue to secure into the printed frame. I used James' color suggestions. The top snaps into the bottom with a few alignment pins, also used PVA to secure the top to the bottom.
I have an OLD bed so the face down printed top piece came out - not smooth. A bit of sandpaper, a few coats of poly and it looks perfect.
Looks FANTASTIC! Works, well according to James it works pretty darn well!
Also working on a pocket sized version (12mm squares)
The author marked this model as their own original creation.