The design will probably work with other whiteboards and other sizes of the staples whiteboards, however it was specifically designed for the Staples 11x14 version.
There are a pair of standoffs which mount to the cardboard back of the whiteboard using superglue, and should be placed either along the sides, or at the top and bottom. They keep the whiteboard from moving too much when using it on the wall.
It prints without supports, and a 3MF is available for it. You can find the models on MakerWorld or Printables.