Either/both of those techniques/measurements would work.
I'm sure if you googled: flying geese quilting
you'd get even more methods.
I think Eleanor Burns has a flying geese ruler/tool that is supposed to be very good. I don't have one, so really don't know.
I would cut 2 1/2 inch strips and work from that. The sky triangles would have not have a point on one of the ends, but would have adequate seam allowance. The "top" point on the "goose" would also be missing, but there would be adequate seam allowance. If one wanted to, one could cut templates with the finished size and trace around them for a couple of pieces to get a feel for how the pieces would be sewn together.