The hub will ask for spokes as needed. The expert indeed draws a picture. Much of this drawing is in the expert's mind. The expert may sketch reminders but a fully drawn diagram evolves in the expert's mind. The novice's sketch is typically so incomplete as to be useless.
Modern technology provides readily available tools for drawing easily.
A well drawn diagram communicates a vast amount of information about the ideas involved in a particular situation. The diagram cannot be executed if the ideas are not known. Just as understanding a problem evolves as the problem solution progresses, the diagram evolves as the problem solution requests additional information. Frequently, students will develop a diagram before anything else is placed on the paper. This is a rote process, not a thinking process.