We made a basic plan of two large pieces, basically two half ovals, one for the upper jaw and one of the lower. I'm planning on having the mouth be wide open, ready to eat little trick or treaters (insert evil laughter here:)) Below, at the scribblings of our plan, the orange, or flat side that will serve as the mouth we measured off at 4 feet. The blue, or dome side, we cut off at just under six feet at 67 inches.
So since neither of us had ever dealt with chicken wire before, our first initial cuttings and forms were somewhat tentative. We eventually ended up laying flat the orange side, and tacking down the blue side at the top and bottom, and one side, then curving half the sides inward to attempt to achieve an oval shape. It ended up looking like a large envelope...or a clam.
The picture of the wire is super hard to figure out wtf it is cause, well, wire. So here's a bit of a color coded picture below to help a bit. So the orange line is the flat piece lying on the ground, the blue piece is in a curve over it. The pink is where we tacked it down with wire, and the green is where we ended up curling in the edges to give it the oval shape.
We had decided it needed some structure to it so that it wouldn't collapse in case the paper mache/paint/etc. got heavy, so we loaded up a garbage back full of balloons and double bagged it in another garbage bag (cause of the sharp wire). So we took the balloon bag and slipped it into the 'envelope' then tacked down the other side, again curling the sides of the wire to go for the oval shape. The second one of these that we did (or rather, the one we picked as having a nicer shape) we deemed the upper jaw (that will have the most form showing) and wired a hook onto the back of the 'head' (the blue side) so that it could be propped up with the use of a bungee cord and held up for display.
Once we had both forms tacked together, we took them onto the porch, just to make sure they fit. And as it turns out--any larger, and it would have invaded the house.