start with a continental grip and find a wall or backboard to start hitting at, close, about 5' away and hit a soft shot, leading with your elbow, keeping your wrist pretty firm.
Lean on to the shot a little, but let the strings do the work at this point.
start backing up a foot or two at a time, hitting with a little more pace, each time. If you can LEAN on the slice, your weight will help make it a more penetrating, skidding shot that your opponents will have a hard time with.
You can also use it to set up a late surprise appearance at the net. Just float it down the line and as your op is concentrating on watching it bounce, follow it to the net for an easy volley.
The slice backhand volley can have as much or MORE pace on it, safely, than a topspin volley. Use your racquet head like a shield at the net, to pick off shots with angles and touch, leaving shots out of reach of your opponent.
Ken Rosewall was the last men's player that had a hard, penetrating slice. Federer rarely puts much on it, these days, since he's fallen in love with his topspin backhand. I watched Johnny Mac play in a Champions Series match and he's hitting a better slice than ever, with a new-tech racquet, strung pretty low in tension.
Also, use it for high kick serve returns. I'm 5'6", when on my feet and used it a lot, years ago, as much as I do now. now.
Yeah, I like the slice backhand..a lot!
Now, ask me about a slice/chip FOREHAND, that's NOT just a "sqwash shot"!