You mark the gap area, on the insulator, then swap them around until they all seat properly.
It's either a total PIA or it works out perfectly the first time. π
Typically there is always ONE that gives you fits, and you might have to buy 8-10 spark plugs in order to get 6 installed properly.....and they ain't cheap.
And that's why you always suspect THAT whenever only one or two cylinders are underperforming on a FICHT or a G2.
Class Dismissed π