Cut cucumbers into slices and/or spears or however you like them. I left the skin on otherwise they get too floppy when pickled.
Combine cucumbers, onions and salt in a large bowl and mix well. Add the ice on top so that the cucumbers are covered and try to weigh the cucumbers down (I used a heavy large plate). Allow mixture to stand for 3 hours.
Rinse and drain the cucumbers and onions thoroughly. (I actually discarded the onions at this point because I did not want an overly oniony taste but most recipes pack them in the jars with the cucumbers).
Combine vinegar, sugar, turmeric, celery seed and mustard seed in a large pot and bring to a boil.
Add the drained cucumbers and bring just to a boil then remove from heat.
When the cucumber-vinegar mixture are cool enough to handle, pack the cucumbers in sterilized jars (use tongs, slotted spoon, or chopsticks). Pour the pickling liquid into the jars, wipe the jars clean, seal and store in the refrigerator.
This recipe had enough cucumbers and vinegar solution to fill one jar that was 0.5L in volume and one jar that was 1.0L in volume (purchased from IKEA) so 1.5L in total.
Bread and Butter Pickles - https://gingerandscotch.com/homemade-pickles-bread-and-butter/