There seem to be loads of names for this sort of card, I've called them W aperature. Might not be as pretty as some of the names but for me it helps stop the confusion.
These designs come as an svg file for the inner aperature fold and like previous designs have minature perforations to create the score line. I do have a template to match the outside but I find it easier to stick them to a larger piece of scored card and trim the outer layer.
The files cost £1 each and at the moment are available in butterfly, flower, bell & bauble. I am working on other designs so if there's a shape you'd like to see as a w aperature or flip card please let me know.