Here's a tutorial on how I make my (pop-up) tunnel cards. I'm showing you an easy way to start things off with, and I'm also giving you some tips on how you can alter the size of the inner piece and so forth :).
by injoystampin
by Artkala
by Little Crafty Pill
by Acrylic Painting Techniques
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by Shilpa Drawing & Craft
by Cheyenne Gonnelly