This holder holds up to 4 buildplates of the A1 type. There's a small recession in the bottom of the slot that holds the protrusion from the buildplate at the bottom perfectly.
I wanted a plate holder that's also nice to look at so I added some decorative features as well :)
You can stack them horizontally if you want (I would also use a dab of glue). The feet are not neccesary but look nice. You can modify the X-Y contour correction for the feet to make them fit more snug (once again, I would advice a dab of glue).
I printed mine with an AMS in black and white, be creative and let me know how you like it! :)