Trees are easy. Just dig a huge hole; at least double the size of the root ball or an extra 2 feet on each side of the ball and below. (Whichever of those two is bigger.)
Then replace the clay you removed with good soil; I mix loam, a bit of fertilizer and peat moss. Add the tree, apply
Myke's around the roots, and fill in the rest of the soil. You want the soil to be a good 6 inches above the roots. Don't get "greedy" with tree height- a healthy tree will grow fast enough.