I really enjoyed making the totem tree. It took me about half a day. I took my time, but what's the hurry? Pressing out the pieces is very satisfying and then building the tree is a similar sensation to doing a jigsaw, only that you are working in 3D. And you don't have to adhere strictly to the pattern, so you can be more creative.
Children under 6 would find it difficult without help from an adult.