Like most others, just leave it off the path a bit, in heather if poss. Sometimes beside a bothy. Even forgotten to lock it sometimes, which shows that it pays not to have too good a bike - it's always been there when I've come back!
(I'll have to go touch wood now: I'll be leaving it this weekend.
Well hidden, double locked, in a cave, sealed up. With CCTV, burglar alarm and electric fence. And booby traps.
)