In this drawing (just send me a mail to get it big size if you will), i explain all the ways of the resin and how to bypass this '"retracting'" thing. the only way is just to mould the base while cutting everything below waterline. The following pictures should help you understand is the idea doesn't speak for itself
Here's another view. You may notice that the glass sheet to which I glued most of the elements is *smaller* than the upper surface, hey, that's because I need some placeon each side to pour the elements! Now you may ask why i didn't glued the elements to the upper glass sheet which will end up being the bottom of my mould? well, that's because I want the final water/resin to be easily unmouldable. This way, i will be able to grease efficiently all the surface.
Then use the bottom of your X Acto knife and press your ball flat on the greased glass surface (you can also use a tile for instance) using some bit of greased transparent plastic to avoid direct contact between the metal and the green stuff -otherwise the green stuff will glue to the metal of course!
Just let dry overnight and detach the stuff from the glass with a blade and that's it! As the green stuff always stays kinda elastic, you won't break anything while cutting them out from the glass surface. The water lillies produced this way are very thin and certainly better than you could find anywhere else -even if using some laser cut paper, and I don't even mention photoetch.