I have another question, this might be tricky

I regularly cast resin figures. At present I use silicon molds. I am considering if it would be possible to print with my Peoplay Phenom using a flexible resin and create a negative mold from my figures .STL I now know how (I think) to slice and split files.

But how do I inverse the selection thus creating the negative space of the figure. So to print the space around the figure leaving a hollow figure space in the middle?

Thank you. You are all amazing and so helpful. In return I intend to sculpt some cool figures, get them scanned and release them for anyone to print if you so wish.

Regards
Sharon

Not sure what slicing software you are using but Ultimaker Cura slicing software has the option to create a mold. You can find it under "Special modes"

If you're using SketchUp, you could make two cubes against eachother and then subtract the model out of the middle of the cubes (half from each cube). Then just pull the two cubes apart and print them separately.
You'd also have to put some holes and pegs and such in there to make sure they stay together when you do the mold, but it should work.

very simple in openscad.
you just import the model and difference it from a cube/sphere/other shape.

Job done - approximately 2 minutes and three lines of script :-)