I am all into making pop-up box cards now a days. These fold flat for mailing, too.
Same card as above but different papers. Sure looks like a whole different card.
Christmas trees and ornaments. A little train going across the front of the box card.
A snow globe box card.
And of course Santa popping out of a box. All of these are from my favorite company. www.svgcuts.com
I use a Silhouette Cameo to cut them out but any die cut machine that can cut .svg files will work.
I left TC to look after all my crafting supplies. Looks like he fell asleep on the job. The shirt by his paw is a birthday card for one of my sons.