Hi,
Ground-layers is my typical way to go.
I let my trees grow bushy, and every now and then I pull one trunk or root-shoot out.
I like to bury a bit deeper my trees when installing them in ground. This allows for the low limbs to root them selves.
That is an insurance for me that even if the tree is sick from being root-bound, it can grow new roots and grow healthy.
I'm happy I did that to my Dauphine. One branch rerooted itself and grew much more healthier than the other branches.
I tried the same with Panaché, but Panaché seems to be a harder rooter. Still the tree looks good.