I have about four or five that I planted last year that I just dug a hole deep enough for the root ball to fit. An inch of soil covering it should be plenty enough.
I gotta tell you, these things REALLY LOVE the shade! I wound up moving them all to complete shade last year because the ones I already had in the shade were out performing the ones in part sun. They create nice foliage and the one that was in complete shade is already about 14 inches wide and 10 inches tall (without the flowers..no flowers on it yet).

I think you did fine....I too planted 5 new bareroot ones this year in addition to the 2 I planted last year...I am hooked on them. And I agree, the blooms seem to be softer, larger and last longer when they are in mostly shade. Most of mine get more sun they I'd like, but I am working on that...planted a redbud and dogwood to create more shade for them.