Cut the cucumbers to desired thickness ¼ to ½ inch; this is up to you and how thick you like your pickles. It is important to cut off the blossom end as it will let off an enzyme that will make your pickles soft.
Place the cucumbers in a colander and rub with the salt.
Place the colander over a bowl or in your sink and let sit for an hour.
After an hour, rinse well under running water for 2 to 3 minutes.
In your pot, add the vinegars, sugars, mustard seed, celery seed, turmeric, and chili flakes if using.
Bring to a boil stirring to dissolve the sugars.
Turn off the heat and let it set while you get your jars ready.
Pack your jars with the rinsed cucumbers and onions.
Pour the brine mixture over the cucumbers and let come to room temperature.
Cover with a lid and place in the refrigerator.
They will last several months in the refrigerator.
Notes
If you want to add some cider vinegar with mother, leave some space at the top and add it after they are cool. The heat will kill the mother, so make sure they are cool before adding it.