Oh, yes! Three inches deep would be good. The mulch on top is very important to keep the roots cool and moist.
Remove any leaves that would end up being buried or they'll just rot and could lead to decay. Probably you won't even have leaves to be worried about but that will happen quickly when it has a new home with you.
Clematises can be drowned by too much water so water well, then wait before you water again. A moisture meter would be a big help.
