Way to draw a template for copying another region

[sammyo]

Not quite sure how to google for this. Say an odd shaped region needs to have the background overlayed, like removing a patch. Is there a way to draw the edge of the patch, but copy the edge to the background, then copy the background within that patch?  I guess I can start to see how a sequence of layers and masks would work but it seems like an option I'm just missing and would be really useful.

Thanks