This game in its various guises goes by several names (some more questionable than others). In its distilled form, Slamwich is a race to see who can whack stacks of cards fastest. The caveats are what makes each round fun—you can only slap the stack when trigger cards are laid down, slapping the stack too early results in a penalty, and muncher and thief cards threaten to steal what you've worked so hard to build.
In this case, a sandwich. Each card (except the thief and muncher cards) looks like a piece of bread or a slice of tomato or some jelly, and players assemble sandwiches by laying down cards between them as quick as they can. When the time comes, they slam the stack. Parents may be worried they'll cream their kiddos, but don't fool yourselves—your motor skills might be more fine-tuned, but the little ones always win.
An interesting variant involves the winner having to eat the last sandwich he ends up with, and while this isn't found in the Slamwich rules and probably classifies as one of those "don't try this at home" things, it's a pretty great way to punish success. Otherwise, just play the regular way, and try to keep violent Slamwiching to a minimum.
How to Play