I've been making some mitered boxes and was looking for a way to get more predictable results, so I did a little research and put together a miter sled and spline jig using various ideas from the web

The miter sled is based on a Mike Pekovich design that simplifies achieving continuous grain wrapping around the outside of the box. He demonstrates the design and use in a FWW article and video. It's a "Members Only" article or I would post a link. It features solid workholding with an adjustable fence and stock clamp and an elevated deck that allows the offcut to drop away from the saw blade. Instead of shop made wooden stops with magnets like Mike's, I just used a couple Rockler flip stops running in T-Track. Mike's is mounted on a couple of Miter Gauges but I just attached a couple of Oak runners to the bottom of mine. The process involves working your way down the length of your board alternating sides: short, long, short, long. Once you get the hang of it, it goes really fast. It is very accurate and more importantly it is very repeatable. The workholding features keep your hands far away from sharp spinning stuff too.






As a companion I whipped up this spline jig from some scraps. It's similar to the many variants you'll find on YouTube, sliding back and forth on the rip fence. I'm planning on another iteration with a larger back diagonal that will serve as a replaceable zero clearance backer for the cut. If I go slow I don't get any blowout now, but better safe than sorry.