Lovi Oy is a Finnish design company designing, producing and marketing Lovi products. The products are made mainly of birch plywood, fits into any standard sized envelope  and the final 3-D shape of the products are made by end users without any special tools. These cards (below) include everything you need: pre-cut pieces and a string with instructions that can turn the cards into any of the 7 different shapes. I like the piggy one.