A quick setup using a light table for the slides (or equivalent evenly diffused backlighting), a mask to keep out stray light, and a Micro-Nikkor or similar capable of flat-field rendition at 1:1 should do the trick.
In order to get decent quality from slides otherwise, you need a dedicated film scanner. Nikon and Minolta made such devices, but price tends to be high and some use (to our times) esoteric connections (SCSI, Firewire and USB devices exist as well). Epson have some USB-connected flatbed scanners that do the job adequately for prints and are not expensive. In their time, Agfa flatbed scanners had a good reputation for quality results (I still have one of their bigger units and although slow, it delivers beautiful copies. It used SCSI).
Whatever solution you end up with, do make sure the work flow is streamlined. It is unbelievably tedious and tiresome to scan slides when these run into the hundreds or more. You need a large disk to keep working copies of the files before they are processed and ready for archiving.