One method to propagate new plants is from root cuttings. This is a thick piece of root that I cut off during the potting  process. I selected a root that showed some nice movment and planted the lower end into bonsai soil. I watered as needed and in 6 month’s time the end of the root sprouted new leaves and stems.

Not all Ficus will grow from root cuttings but one fig that does particularly well is Ficus tremula.

Left root cutting, middle same cutting after 6 months, right trimmed back to start the bonsai training