It is very simple, works well with all Apple cultivars, Cherries, Plums, Peaches, Nectarines and Pears. Many ornamentals may also be propagated by this method - Rhododendrons, Camellias, Wisterias and some difficult Conifers not easily produced by cuttings....
...I have noted over the years, that some plants, however reluctant to provide themselves with their own roots, will do so if a small root-piece is inserted at the bottom of them. In this case, wounding and application of rooting hormone will also help.
Others will produce roots better only on succulent successive young growth. You plant the graft at soil level and as the young growth starts, cover it with more soil so that the young roots can develop on the new growth. In this case the graft becomes a 'nurse graft'. Eventually the initial root may completely disappear.
When you are sure that this will occur on a particular plant, then you can use a rubber tie, this will strangle the initial root and allow the young plant to develop their own roots.