The HC version of Havoc’s Call should be on the back of the character.
Currently it’s on the character’s side like a regular weapon.
On WoWHead there are a few screenshots about the weapon: https://www.wowhead.com/item=50737/havocs-call-blade-of-lordaeron-kings#screenshots:id=267098
Also that’s how it works on retail too, it’s on the character’s back.
EDIT: I have HC Havoc’s call on Rogue, no idea if it’s different for other classes.