Jigs, are definitely the best. Particularly for production runs. Optical alignment is quite amazing but slower than a jig since there is no figuring out time, it’s just load and go. I often tape the jig down to the tray sides or the bottom of the machine with blue painter’s tape off-cut, so the jig won’t move. it’s a little trickier if your object is weirdly shaped in Z like a spoon or something. Then you have to find sort of the perfect touch points for your jig so the spoon repeatably drops to the same spot. When I’ve done even short runs of stuff (like a dozen) I use a jig since who has time for all that figuring out stuff… that way text is always square, etc. also if your part needs th4 tray removed, you can of course build your jig as a 3D jig (yes, all jigs are 3D but you know what I mean) I mean if you’re doing 3 of something a 3D jigs is a lot of work, but if you’re doing 20, it’s a huge time saver. I’ve used jigs even with snap marks particularly for weird objects.
As an example of jigs, when I did the sweat scrapers at the barn last Christmas (they were spline curves) so needed something to hold them at the correct angle.