I don't know this technique but you have piqued my curiosity.
More info?
I know where you can buy pure coconut soap? Health food stores carry it.
I found the technique. I couldn't wait. I am pretty sure this is it:
Splitcoaststampers - Tutorials
I think the soap is melt and pour coconut base. You could probably find that at your craft store in the soap making section. You can use health food store soap too.