This article is from the Food Preserving FAQ, by Eric Decker email@example.com with numerous contributions by others.
From: Robb Dabbs
There's an old trick used in the South to reduce salt in country ham
(which is salt cured), and it should work for your frozen ham. Thaw
the ham, cut in slices if not already sliced, and soak overnight
covered in milk. Next day, rinse and pat dry, and prepare as desired.
I don't know of any different storage method that would prevent the
saltiness from occurring.