wesing, yes, the backing is Stonehenge.
toogie, it's a copy of a pattern's picture that was posted on the Board in 2013. The HSTs are 3" finished, and everything else is multiples of 3".
Watson, oh, I couldn't possibly do it freehand! I traced the pattern on Golden Threads paper and quilted over that. Time-consuming, but the only way I know how to do it.