It is usually already frozen and it is usually frozen already are equally fine.
I agree with mpre53. Usually could be in either position
I agree, it could be in either position but usually frozen already sounds better to my native English speaker's ear.
I'm also a native English speaker and I'd say "It's usually already frozen." If I wanted to put it after "frozen", I'd probably change it to "by now".
Yleensä = generally
'Generally' would be better translated as yleisesti (ottaen).
Why would usually it is already frozen be wrong?