Been mulling over different designs from the simple one with a wood spacer to versions with gears or ratchets and plenty in between. Stumbled across this jig by Mario Cappellano for a single blade and knew it was the right one for me. Pretty simple, the wood to be cut slides left and right across the jig, a pin the size of your saw kerf rides between spacers the size of your box joints (whatever size you want). Simple to build, simple to use, simple to change box joint sizes (just make new spacers). Since it uses a single blade it's not fast compared to a dado setup but not everyone owns a dado blade and not every saw can use a dado blade. I made a few minor changes, most obvious is I added a handle. More details and pictures here, if interested.
