How do you wear a longbow across your back?

I'm doing some research into the use of the longbow from the 1200s-1400s and am curious about how archers would carry their longbows when walking or riding a horse. Obviously it couldn't always be in their hand, and I've seen depictions of longbows worn across their backs. How was this done? Was there a holster for it, or were the bows simply looped across the quiver or the shoulder? Were they strung, or not?

Also, how would you make the string for your longbow if you were a woodsman from this time period?

Thanks!