What's a quick way to turn on the torch?
Theres a Torch app in the market that toggles on open. 

Do you want a single button on home screen? Then you need to shortcut it.

Do you need it on your lock screen: swipe for widgets.

Do you need it on voice activation? "Ok google, open app flashlight/torch"

Do you want it on your shortcut bar? Drag it from programs.

Im not really sure what you want.