I was just over on WoodNet, reading a posting called How to clamp 135-degree joint? Near the end of the thread, there's a posting by ezflier with a link to a web page by WoodNet's own Edwin Hackleman. Edwin is a very intelligent guy who seems to delight in geometric puzzles and how to make them with the simplest possible set ups.
The page in question describes the Bird's Mouth Joint. This is a joint specifically designed to simplify cutting & putting together 8 boards to form an octagon. While I'm not building an octagon, the angle at which the face frame meets the "sides" of the corner cabinet is exactly the same. This joint looks like it will be easier to cut. Let me explain why.
Originally, I was planning to cut 67.5° miters on the edges of the side boards & the face frame stiles. I don't know about you, but I don't have any precise 22.5° or 67.5° reference angles lying around, and I don't know where you'd find any. So there would be a lot of trial and error cutting of scrap to get the saw blade beveled to the right angle.
You then have to glue these boards to each other. I had come up with a clamping caul and had posted a picture of it in that thread. As Ms. Nomer says in the thread, there might be a problem with this configuration not providing enough clamping pressure to keep the mitered edges up against each other.
The bird's mouth joint, on the other hand, looks pretty easy to glue-up. The angled board essentially sits in a socket & is self-aligning. All you have to do is clamp a beveled block to the angled piece, then run a clamp horizontally. And you're done!
So I'm gonna give this a shot using some poplar scraps I have lying around at home tomorrow night. Tonight, I'm going to WoodCraft after work & use their jointer. And maybe a table saw to make sure I have all the edges straight & parallel. Or maybe I'll do the ripping another night at home. Let's see how busy the place is.