It's worth bearing in mind the access to this nut:
It's recessed into the sprocket, (this is compounded if you use the secondary chain as a means to restrain rotation during removal / installation).
If you have a FERC configured bike the forward section of the FERC has to be installed before the sprocket and thus recesses the nut even further.
The above result in a plate spanner only being able to partially engage at best.
The extension of the main shaft through the nut precludes a normal design socket from fitting, the thickness of the nut also renders an unmodified socket engagement to around 50%
£12 for the correct box spanner is money well spent in my opinion