I did this last year and it worked great!!! Not a whole lot of work either. I just used a foam ice chest and made a frame with chicken wire and paper mache to fit right over it. If time is an issue perhaps a prefab rock like evil eyes suggested would be even better!! This is how the rocks turned out
DekoRRa just released this new line of fake rocks under the 117 Model. Great looking fake rocks with beautiful texture and colors. The one i saw was riverbed color and it looked incredibly real. These are made to cover cable boxes and other utilities.
www.mooreconcepts.homestead.com Richard Moore takes you through step by step making Artificial Rocks with Concrete. The potential is endless - waterfalls, large rocks, small rocks, natural steps and more! All you need is concrete, oxides and some basic tools like spoons, knife and paintbrush. Richard is based in Maungaturoto, New Zealand.