Referenced from : http://www.iphonedevsdk.com/forum/iphone-sdk-development/8349-how-get-vertical-slider.html
UISlider *uiSlider = [[UISlider alloc] init];
uiSlider.transform = CGAffineTransformMakeRotation(-90.0/180*M_PI);
or
uiSlider.transform = CGAffineTransformMakeRotation(270/180*M_PI);