Here are your free printables:
Of course, it is preferable to make this card on a digital cutting machine (with the .svg file). The tear strip perforations are pretty fiddly to cut out with a craft knife. Aside from cutting the tear strip, making the card is a doddle. The front cover is fixed onto the card blank like so, using strategically-placed strips of d/s tape:
Remember to remove the little piece of paper to the left of the tab on the tear-strip (shown above). Print the card liner on thinner paper - cheap-o photocopier paper will do (the card itself is made from 160gsm photocopier card). When presenting the card, I like to raise the tab just a smidge as a prompt.
And of course, you can edit the text to customize your secret message.