How to Hollow out a mask?

I’m making a 20” head to sit on a mannequin for Halloween. I used Meshy 6 to create the file and took it to Meshmaker to make it hollow. When I bring it over to bambu, I set the infill to 0 but it’s not hollow. I tried using ChatGPT and it left me with the same thing. I searched previous topics but didn’t see anything relevant. Any help is appreciated.

I assume that it being 20” in size you cutting it into parts? Are you making hollow before you cut it into pieces?

Yes, I’m using mesh maker and hollowing the whole image. Then sending to Bambu to scale and cut.