This took a minute, max, to code in GNU Smalltalk and even less again to rewrite in Squeak - which I had to do, after several hours of failing to install GNU Smalltalk on my Slicehost slice. I followed that up with a few hours of failing to install Squeak on my Slicehost slice. Finally I resorted to Seaside Hosting, which was quick and painless.
I was already uploading to Seaside Hosting when Monty Williams told me about this blog post explaining how to set up Gemstone GLASS on Slicehost. That's what I'll use next time.