Hi,
Is the tree growing bushy, with several root-shoots ?
If it is the case, just set a ground layer - that is the easiest to do.
With the cuttings that you have, this time of the year, I simply put them in loam (dirt from the nurseries) in gallon pots outside in the garden and I let them do.
Most of the time they start growing a bit later than normal, but they grow healthy .
Patience, and good luck !