Cut cucumbers into a mix of spears and slices. Layer the cucumbers and onions with the pickling salt and ice in a large bowl or pot. Put in the refrigerator and let chill for 2-4 hours.
Rinse the cucumbers and onions thoroughly under cold water and drain well.
In a large pot, combine the vinegar, sugar, turmeric, celery seed, and mustard seeds. Bring to a boil, stirring until the sugar dissolves.
Add the drained cucumbers and onions to the boiling brine. Return to a boil, then remove from heat.
Pack the hot pickles and onions into sterilized jars — some spears, some slices. Optional: add a garlic clove or a jalapeño to a jar or two for variation.
Ladle the hot brine over the pickles, leaving about 1/2 inch headspace. Wipe rims, seal with lids, and process in a boiling water bath — 10 minutes for pints/half-pints, 15 minutes for quarts.