One of the oldest preserved Christmas hearts were made by the fairy-tale author Hans Christian Andersen in the 1860s. An old Danish tradition is to cut shiny paper and braid the hearts and use them as ornaments on the Christmas tree. With these templates, you can try yourself.
See a guide here for how to braid them, and even for how to design them yourself (made by Torben Mogensen, not me):
http://hjemmesider.diku.dk/~torbenm/hearts.pdf
To get the texture of the printed templates as seen in the photo, set top and bottom layers to 0, and infill percentage to at least 20%.
The author marked this model as their own original creation.