Taking cuttings is one of the best ways to start a bonsai tree. In this example a cutting of Ficus ‘Mystery’ was taken. It was a long straight piece of stem with several aerial roots. A cutting taken with aerial roots is almost guaranteed to root.
In this case the cutting rooted successfully and several years later the bonsai created was an attractive semi-cascade tree.
I take cuttings regularly and place them in bonsai soil and enclose the pot and cutting in a plastic bag to keep the humidity high. The bag is kept out of direct sunlight but in good bright light. Open the bat and water the soil as needed to keep the soil from getting dry but do not keep the soil totally full of water.