Usage patterns
〈物〉のおにぎりonigiri with a certain filling
I like onigiri with pickled plum filling.
おにぎりを握るto shape/make a rice ball by hand
My mother shaped rice balls for me early in the morning.
おにぎりを包むto wrap a rice ball (e.g. in nori or plastic wrap)
I wrapped the rice ball in nori seaweed.