Is there an alternative to using an ice cream maker, as I don't have one.

I was just going to post that same link! I used David Lebovitz's technique a number of times before getting an ice cream maker, and it works pretty well on the whole.

David Lebovitz walks you through how to make ice cream (and frozen yogurt) without a machine: http://www.davidlebovitz.com/2007/07/making-ice-crea-1/