In the comments to yesterday's post on the R'lyeh calendar stone the subject of producing a similar artifact on a DIY basis came up. Alex Kaeda brought up the idea of carving one out of foam and then linked to this tutorial on using exactly that technique to recreate the Grail Tablet from "Indiana Jones and the Last Crusade".
Foam would be ideal for creating a similar Lovecraftian item, but I suspect it would take a great deal of patience to carve away the fine detail work. I used carved foam to create the backdrop for my collection of items from "The Shadow Out of Time" and the results were pretty good for a relatively quick project. As I mentioned at the time, one of the nice things about working with foam sheets is the sheer amount of material you get for the money. I still have a huge chunk of the stuff in my closet from that effort.