How to make my own 3.5mm dual audio cable?

I want to make my own 3.5mm duel sided audio jack/cable out of old cables or headphones. Only need it one sided though so I guess it's now a dual. I want it so I can connect one side to sterio speakers by wires then I can plug the other side into my iPhone. Without buying the cord and cutting it how could I do this?

You don't. FAR cheaper to just buy one.

Why spend the time and effort when you can get it done for 89 cents from here: http://www.firefold.com/35mm-adapter-two-jacks-plug?afid=60