stencil cake

Hi im new on the forum so apologies in advance if I mess up.
I was wanting to make a cake with white fondant rolled over it.
I hsve been asked to make tje picture of a celeb ontop of the cake. Somebody suggested making a stencil abd using a sieve and cocoa to make thw face. ..im not sure how this will work..

Can any1 help?

Thsnk you.
P.s is there an app for this site??