Prints fine without supports, the cardholder lid is a press fit into the main case.
These cases are intended to be used with a PiZero (Or PiZero2w) and can be connected either using a GPIO splitter or by adding right-angle headers on the underside of the board. (You will need to use the appropriate model, see pictures for wiring info)
The author remixed this model.
Adjust to accommodate a PN532 module.