I start with a curvy line, spine around the entire quilt, then do 'bump back' petals on the right side, all the way around, and once I've come all the way around, i do the left side the same. Occasionally, I'll add a swirl or something to fill in a gap, but mostly just differing sizes of petals to fill the sides.
On one quilt, I worked out making two ropes of feathers intertwine. It was fun, but nerve wracking.
https://www.pinterest.com/pin/535083999460677467/. It's a wide border on a Radiant Star quilt.