In a large bowl combine the cucumbers and onion, sprinkle with salt, and toss well. Add the ice cubes and chill, covered, overnight.
Drain the mixture in a colander and rinse under cold water. In a saucepan bring the remaining ingredients to a boil, stirring. Add the cucumbers and onions and bring to just a simmer, stirring. Transfer to a bowl and cool. Chill the pickles, covered, for 24 hours.
The pickles can be made 1 week ahead and kept refrigerated, covered. Or, spoon the hot pickles into sterilized 1-pint Mason-type jars, filling the jars to within 1/2-inch of the top. Seal with the lids. Put the jars on a rack in a kettle and pour in enough hot water to cover them by 2 inches. Bring to a boil and cook, covered, for 10 minutes. Transfer the jars with tongs to a rack and cool. Store in a cool, dark, dry place.