Fall through winter is a great time for evergreens. I put them in a draining tub placed out in the elements, protected from wind by the vented cover, and from excess sun by the frosted or white quality of it. Mother Nature does the rest. The trick with arborvitae, and perhaps many other similar plants, is to keep the 'heel' attached at the base of the cutting: that place where the green sprig connects/ed to the brown stem. Even tiny cuttings can root when they retain part of the brown stem at their base.
Best wishes!
