I may be wrong ,but when I am planting any new clematis I always dig hole a little bit deeper than size of pot plant is growing in.

And cover base of plant with a tile to keep roots cool.

That's not wrong, Kath - it's spot on because if the plant then suffers from Clematis wilt, there's every chance that it might send up new shoots from below.
This particular Clematis doesn't like cold winds - so plant it in a sheltered but sunny position.