I've found I can get really nice results scanning slides by
backlighting the slides with one of these cluster flourescent lamps
about 4-5 inches above the slide, with the slide isolated in a window
cut out of black craft foam and for a light diffuser the lid of a
tupperware type container and then a flat piece made out of cured
clear silicone caulk over that. This seems to produce images that are
sharp and evenly lit.

I'm wondering if there are any steps I can take to refine the process
further to get even better results?

Any suggestions?

Thanks