Yes -- I use them. They're not precisely cheap but if you collect a few over time, you'll have what you need. They do need to be stacked 2 blocks high, I discovered.

You can see the start of one bed on my blog, sort of near the bottom. My blog is Alla's Little Acorn at Blogspot, if links don't work right. There's a photo of the first bed in a new spot, and an explanation of why I tried this, and yes indeedy, it does work nicely.

http://allalittleacorn.blogspot.com/

Here is a link that might be useful: Alla's Little Acorn