Quick Question, Simple Latex Skin

[travsall ●]

I was going to send a PM to a couple guys, but thought this might be something other members would like to know about too, so thought I'd start a topic. I'm trying to make just a simple thin latex skin for a costume, a zombie costume, basically I need a roughly 12" squared piece of thin latex that I can add some damage to, attach to an under shirt and paint to use under a top shirt. My question, what's the best, easiest way to do this? All I have for latex is a jar of mold builder, but it can be thinned etc for whatever purpose, my main quandary involves what to pour the latex into while it's setting up, some kind of simple tray etc that it won't stick to, and will produce a good enough pull.