To de-sand: Make plenty of 3% saline solution. Rinse the clams and line them on a shallow tray with some space in between. Pour in the saline solution until the clams are mostly submerged, cover with newspaper and leave in a cool, dark place overnight, occasionally changing the water. Rinse again afterward.
To de-salt: Rinse the de-sanded clams, and line them on a colander or a tray without overlapping. Cover with wet paper towel and leave them in a cool place for 3 hours.