How to model a footprint / mold

Hi @DaveR !

Thanks a lot for your answer.
This would work in hunderds of situation !

Would you have some sugestions to keep the “3D” shape of the below surface ?
I agree for this pair of plier, this would work just fine. A couple of notches here and there to make it easy to take it out.
But in some cases, I would like to keep the “3D” shape (or organic shape, let’s say !) of the faces below.
To give an example : let’s say I would like to put a SLR camera with its lense entirely (not half way) in a block of foam. For the body of the camera, the bottom can be flat, no problems ! But for the lense I would like to keep the shape, so it would be supported.

Any ideas ?