Have you been desperate to put aerial roots on your Ficus? Have all the usual tricks failed? Have you gotten poor or weak aerial roots that are in the wrong places and at the wrong angles.
Recently I found a technique that seems superior to other techniques that I have tried.
First, remove or obtain some fresh long roots from the Ficus species that you wish to graft. In my case I was repotting a Ficus salicaria. I removed four long unnecessary roots, and these were used immediately and were not allowed to dry out. The roots were from the same tree but probably roots of the same species would be fine as well. If using roots from another species the bark character may not be similar and therefore the roots will look out of place.
I simply planted several inches of the roots end into the pot in the exact spot were they were wanted. I then notched the underside of the branch on the mother tree and inserted the other, cut end of the root. Make the notch or hole in the branch slightly smaller than the root's diameter. Then cut paste around the joint graft, but be careful not to wiggle it apart. For stability wire the new aerial root joint. This protects the joined areas from moving in the wind or from being bumped when watering. Within sixty days you will find the root has taken by its increasing girth. If the graft fails the root will shrivel up. Once the root has taken the protection wire may be removed. The successful root wll be in the right spot and at the right angle. If the grafts do not succeed then get some more roots and try it again, you have not lost anything but a few worthless extra roots.
On my Ficus salicaria , I grafted four roots, and two succeeded despite the fact that this was done in the fall when growth is not optimum. I would recommend this be done when growth is most rapid, and suggest avoiding thin roots as they will dry out before they can take. Aerial roots can be grafted in the same way and are even more likely to take hold.
Another technique is to use a small seedling fig to graft into the host tree exactly where a new aerial root is required. Use a modification of the above process and cut off the foliage once growth is apparent. This usually takes about 90 days.