The first copier I built was fine for one at a time, but I have trays and trays and trays... It would take way too long to copy them that way. So I needed some sort of handler to feed them through.
The solution was to take one of my old slide viewers and remove the lenses, so the camera could have a straight shot at the slide. I fabricated the stand out of some scrap bits I had laying around the shop. With my old S602z mounted, I was in business. See my "Back In The Day" gallery.
I am currently using the same backlight that came with the viewer. Not ideal, there is a slight irregularity in it that shows up if I have a lot of light featureless area in a slide, like a bright sky. And on some slides it looks like I'm losing some light on the sides and corners. Others look fine. If it gets too annoying I'll consider a redsign of the lighting.
For shooting, I set a custom white balance off the backlight, and used aperture priority mode. I'm still experimenting with what f stop works best. The camera was positioned as close as I could get where the autofocus would still work. On the S602z, I used the "medium" macro setting, and zoomed out to the max. YMMV. They only need slight touches in post processing, a bit of contrast reduction sometimes, and cropping to taste...