Trying to make Glass Fiber access panel

[pcoghlan]

So I have a square access hole in the transmission tunnel through which I can perform various maintenance chores. Bleeding the clutch, etc etc. The car is very snug around the frame and transmission and so this was a near mandatory requirement.

I now need to make up a cover to go over this access hole and am trying to work out how to do this...

I have the matting and resin but how can I make a simple square panel without it sticking to whatever I make it on top of? There must surely be a simple material I can lay the resin/matting on that it wont stick to? I hope this makes sense. The wife suggested saran wrap, make sense?

Thanks,
Paul