Pop-Out Stacks Base DiesThe Pop Out Stacks Base Dies create a fun, dimensional card base that folds flat to fit inside an envelope so you can send some extra special happy mail! The Boardwalk Stacks and Secret Garden Stacks Bundle have been specially designed to use alongside these dies, but you can also pair them with any number of items you have in your crafty stash. 4 pieces. Click here for written instructions on how to assemble the pop out base.