Bit of dowelling with masking tape round it, put layers on till it matches the diameter of the hole, then use it to line it up, do the pressure plate bolts up just enough to hold the clutch plate so it can be moved but then holds it again once aligned.
But the box in and trial fit it to the clutch, once the spines line up it'll go home, then take it off again very carefully so as not to disturb the clutch plate position then tighten up the pressure plate bolts to the correct torque. You'll only need to move it back a tiny bit.
But all of the methods mentioned above will work. It ain't rocket science!