First of all, can I just say this shape is not attributed to me. I started by cutting a blank 15 cm x 30 cm and scoring down half way. Then scored the front diagonally from the top left to the bottom centre line.
Now crease so when stood up it looks like this.
Cut another square 15 cm x 15 cm and use as the topper and attach to the triangle piece.
Easy when you know how!
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