Okay, it took me a while, but I finally found it! The lady who wrote the tutorial is currently in the process of moving all of her blog content from her free one to her hosted one, but she agreed to post the tut for me even though she is still working out some of the kinks in the site. So if you see some weird page formatting briefly, it is because she is still designing her blog.
http://www.emilyedesigns.com/3d-print-ring-forms/
If I read the bottom of the post correctly, she will also design the ring forms for you at any width and thickness you want for $4 if you don’t want to (or can’t seem to) design them yourself.