Once upon a time, in a galaxy close to this one, so close in fact, it probably was this one, there was a card swap that I joined. The theme was pop-up cards. The theme had been suggested by someone who felt some oldie but goodie techniques should be re-visited. And indeed they should.
How did you learn about pop-up cards? There seems to be two different camps on that. One bunch of folks, like me, learned to make slits in your card that crossed the center line. Then you popped that section the opposite way of the card fold and attached whatever image you were popping up onto it. That did mean your card was two layers thick--the outer layer and the inner layer that you cut slits into. The other camp was made up of people who used strips of cardstock to fold up boxes or rectangles to glue into the inside of the card. Those, too, had the image to pop up glued onto them. That made for a one layer card as your card base had no cuts in it.
Then came the advent of multipe cuts into your card to create an entire tiered staircase effect. You could even buy pre-cut cards for that (DeNami comes to mind). Then there were side fold card with interesting cuts to make popped out shapes, such as a heart. Then came Pop-Ups by Plane Class. They were brass stencils that you centered over the crease of your card and painstakingly cut out sections so the popped up section spelled a word like so:
The Fine Print: I admit that my theology may be a bit off. Fancy paper by Imaginisce, corner and bornder punches by Martha, celebrate die by Pop-dies.com, flower punch by Stampin' Up, circle punches and butterfly punch by EK Success, Happy Birthday by Penny Black, flowers by unknown. Devil Cat by God, made on a day He should have taken off. I feel, indeed, an excessive use of commas happened in this post. And, for that, I apologize.