Printing/sublimating on an odd object, a circle with a inset and sunken face. How do I properly adhere the sublimation paper?

Hello r/Sublimation, I am looking at something I haven't seen any widely available tips on.

I am trying to sublimate an image onto a 3d print, which is a coin that has an inset and depressed inwards/down face that is 40mm in diameter. The issue I run into is the rim of the coin preventing my heat press from accessing the sublimation paper. How do I get a heat press in there??? It's driving me nuts! Is there a tool I can buy to help with this?