I have never made my leaves that thick or used any chicken wire for reinforcement. Two inches of concrete is pretty thick but obviously there are many ways to do it.
I also want to warn in using like Dan said a scraper or chisel to get the leaves off the concrete for the finished product: this concrete is by far NOT totally cured. Two days for 2 inch thick concrete, going at the vein design would chip off and ruin the decorative part of the leaf. My leaves cure for 3 days or 4 (depends on humidity) and they are covered with garbage bags to dry slow to prevent cracking--the leaf is peeled off--then put back into the bags for a few more days. They should be ready to paint after that and won't be ready to use a clear coat sealer for a few weeks. I was also surprised that he took the cement all the way to the end of the leaf: once the cement goes over the edge, it becomes thin and can break off (like the edges of plastic in a mold).
I would have liked to see his finished leaf...