Long story short:

It's made from four pieces of a light foam fibreboard and about 5 feet wide by 4 feet tall. I googled for "old tree" because I wanted something that looked windswept and most importantly, had very few leaves. I wound up using this painting. I then drew the outline onto the fibreboard and cut it out. I had a exacto knife but I actually found that simply pressing the pencil deep worked well most of the time, and was also easier around corners.
Here's a close-up:

I drew over this one so you could see more easily where the intersections between the four pieces are:

I was going to use the pencil to make indentations for woodgrain, but decided to leave well enough alone. I flipped the pieces over to hide the pencil marks (that's why it mirrors the painting) and just stuck it up there with copious amounts of scotch tape. Sometimes I think it's a little creepy looking - the black leafless branches kind of remind me of that scene in Snow White where the trees grab at her - but most of the time I really like it.











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BUT, I love my box, and I can't believe how crammed it was! As soon as I saw how much it was bulging I was excited. 





















