Thread Grafting
Let it grow, let it grow, let it grow!
The process may take 1-3 years, and requires a healthy tree. Allow at least one shoot to grow very long.
A shoot near the apex will be the most vigorous.
When
Most tree species should be grafted late winter, just before the buds start to swell - this applies to both thread- and scion grafting. Approach grafting should be performed in summer however.
Michael Hagedorn blog
The bark of deciduous trees like Stewartia is so thin that it grafts easily without removal of any tissue on the scion, and removal can damage the small seedling. For most approach grafts of deciduous trees I don’t take tissue off the scion, on approach or thread graft.