This "never-ending" card is a variation on the one we did in 2013 (which featured a Santa in four different sets of clothes). That card used two double-sided sheets and changed shape as it was opened. Some areas appeared on more than one side in different orientations. As that would have broken up complete pictures, we used separate motifs in those areas and hoped no one would notice they had turned!
The method below uses four one-sided cards instead and restores the integrity and shape of all the four printed faces as the final card is turned. I think it's a little easier to see what's going in this card -- I hope that won't destroy the magic!
We've chosen two landscape pictures and two portrait ones for this card. This is purely because all the pictures stand up properly for display this way.
Here's how we made this one ...
Take four sheets of A6-sized card and cut each in half as shown (two cut one way and two the other):
Take the first card, open it out from the middle and lay flat with the plain side upwards:
Glue the corners (you may want to mark out the whole card into a regular four-by-four grid first). Then place on top and stick down one of the other cards that is cut the other way:
When the glue is stuck, fold back the top card as shown and crease the folds:
Now glue again, this time missing the four cells on the grid that are show with crosses, and glue on the next image (alternating orientation of cut):
When the glue is stuck, fold out symmetrically and crease:
Now glue the entire area and stick the final card on top:
When dry, open and crease all the joints:
The finished card should stand up sturdily with any of the four cards showing at the front and its opening should be never-ending.
Enjoy!