This topic was covered a while, may want to check out the old threads on softball drills. You Tube has some videos of sliding drills, using two sheets of cardboard and also sliding on a wet tarp. With my DD's, I took them down to the ballfields when the infield was damp from rain but not slick, had them slide into the base from about 10-15 feet, after a while, seemed to get it. Also, her peers were sliding well so that was additional motivation for her.