I put a 5DS camera on a copy stand. I put an old lightbox on the copy stand's board. I use a slide holder from my flatbed scanner, placed on the lightbox. I attach a remote switch to the camera so I don't have to touch the camera for activating the shutter. The lens is a Canon macro dedicated prime (100 fl). Auto focus is activated. Some prefer doing a manual focus. I don't like touching the camera or lens after it is leveled. The lens IS is activated. Some prefer the opposite. Since I prefer using the viewfinder to check focus and not live view, I place a small circle bubble level on the LCD. This helps me level the camera before shooting the slides. I also watch the level's bubble when I press the shutter button on the remote. If the bubble moves (which rarely happens) I do a second shot.
I prefer processing RAW files rather than TIF or JPEGs because RAW is more versatile. That is why I prefer camera to scanner.
Slide cleaning: First I use a camel hair, angled brush that is 3/4 inch wide. I think the art world calls it a shader brush. Next I use a rocket blower.
I also use an old slide viewer to cull which slides to copy. Camera or scanner, making digital copies of slides consumes time.
I set the lens aperture at f11 and ISO at 400. I found little difference between ISO 100 and 400.
For those who wonder why I do the above as described it just my preference and it works for me. Winter is my slide copy time.