Interlocking items for printing

I’m trying to create a sculpt for printing. I have a character face that I’d like to be able to put a mask on. I am using the app on my phone. I want to, functionally, invert the shape of my character’s face, then sculpt on top of it without altering it, to make mask piece. is this possible? thanks!

A possibility: use select mask to select the portion of the face you want to use, then extract a shell from the selection with the closing action.

I’m pretty sure @Holger_Schoenischka has a video covering how to do this. maybe he can provide a link when he sees this. This one probably covers what you would need to know:

Note that there is also an offset option, which may help with getting a sufficient gap to make it work with printing:

Could maybe make the mask, duplicate the face, overlap the mask/face how you want it to fit then boolean so it’s perfect. I’m new to Nomad so hopefully the veteran sculptors will correct me if I’m off.