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This is a charming little box for St. Patrick's day -- when opened, it has a delightful reveal.
It is made from a scalloped octagon, a thoroughly impure medium for origami. (Most folders eschew anything that is not square. Some of the broader-minded origamistas will allow for the use of convex polygons. No one will sanction this shape.) A piece of letter paper will yield a box 2¼ inches (5.71cm) wide. Here, I've blown up the model at a local print shop,so it looks a little bigger.
Step 1: Grab the File
Here you are, a nice PDF of the Guinness Box model. As you can see, the shape is that of a scalloped octagon. Print this and then cut it out -- extra points for accuracy, here. Cutting around the scallops can be persnickety.
Also included here, for your edification and maybe pleasure, is a PDF of the model without all the artwork. This is CC stuff -- feel free to whup up your own boxes.
Step 2: Precreasing
There are several conventions for the representation of mountain and valley folds. Here, the mountains are solid black lines and the valley folds are solid magenta lines. The gray ghost lines are for reference only and may be safely ignored. Fold accordingly.
If you're not sure about the distinction between mountain and valley, try here
Step 3: Collapsing
This is how it looks as you begin to collapse the model. The scallops will begin to stack up on top of each other.
Step 4: Locking
This is the cool bit -- the top of this box is slightly wider than the base. Put your finger in the center and push -- gently, now -- straight down. There will be a noticeable popping sensation as the model locks shut.