That is quite some hill if a ball will not stay still on a grass surface?!?!
Laws state ball must be stationary. I am not sure what common sense dictates in this situation? Find a pitch which isn't on the side of Ben Nevis?
If it is that bad have another player (or the taker) hold it still until the kick is taken? Just guesses as there appears to be nothing in the good book about this sort of situation. Any Guidance from local RA or league about it?
Had a former football league ref tell us a story at my local RA meeting, the wind was so bad that the had to get a player to hold it to take a corner. Someone asked if after it was taken he penalised for handball,
There was a ground in my area where the difference in height from one corner to the other (diagonally) was 14ft (3.5m?). It was a common joke that if an assistant went down to the corner flag for any reason he wasn't coming back out again!