Originally, natives made bowls and baskets from birch bark to collect berries and for storage. They were left behind when the tribe moved on. They decorated the ones used for special occasions. It was a very eco-friendly system-- they ate the porcupines and decorated the boxes and baskets with the quills so nothing was wasted.
Today, porcupines are no longer used for food. Their quills are obtained by throwing a blanket over a porcupine-- the quills stick in the blanket, and the artist literally has a sheet of quills with which to work.