Do what a geekchic does!
Take out your trusty toolbox. Root around for a testpen. Sanitize it the best you can: Wash it with anti-bacterial soap. Rinse it clean. Repeat. Drizzle hot boiling water all over the metal tip. Fling it dry. Gently pry one corner loose. With one corner out loose in the middle, slowly and gently tap or knock the sides of the box. Loosening one piece breaks the "foundation" of the cake and the rest of the pieces would come loose very easily from the vibration created.
There's something highly satisfying from using up every single bit of the product before opening up a new box.