It can be a expensive as you want to spend, but cheap is another story....
Scanning is basically taking a digital photo of a small item that needs to be lit from behind. So in all reality, if your smart phone had no distortion and could focus that close, you could get a "Picture" of the slide, I have done that at times.
Now, of course the aspect of quality comes into play, do you want to text it to a friend to give him a laugh or make a high end 30x40 from it?
I use my D800 with a macro lens over a light table to do quick and dirty "scans" that actually come close to my sophisticated and dedicated Nikon 9000ED scanner for output that is smaller than say, 11x14, certainly enough to evaluate a shot or post it to the web. A lesser MP count camera would be more than adequate for most small prints and web as long as you use RAW. You could rent the D800 and a 60 macro from Lensrentals, borrow or improvise a small light table and be well on your way, just sort the slides by color cast, density and shoot them in a logical order. Make a mask to prevent flare by cutting an area the size of the film in a piece of black construction paper.
Other people use flatbed scanners like the one currently listed in the classifieds. When you want to obtain a digital representation of a piece of film, you are essentially taking the photo again with some limits, I wish I had a better answer for you but ultimately, your budget will dictate what you go for, if anything at all....