Wash the cucumbers thoroughly and slice into 1/4-inch rounds.
Place the cucumbers, onion slices, and jalapeño slices into a large bowl. Sprinkle with kosher salt and mix thoroughly.
Cover with plastic wrap and refrigerate for 4 hours, stirring a couple of times during the brining process.
Drain the vegetables and rinse thoroughly under cool water to remove most of the salt. Drain well.
In a deep saucepan, combine sugar, vinegar, water, garlic, mustard seed, celery seeds, black peppercorns, turmeric, and cloves. Stir and bring to a gentle boil.
Reduce heat and simmer for 3 minutes to allow the flavors to combine.
Add the cucumber, onion, and jalapeño slices to the pot. Bring back to a gentle simmer and cook for 2–3 minutes.
Remove from heat and allow the mixture to cool.
Transfer pickles and brine into clean glass jars. Store in the refrigerator for best flavor, allowing 1–2 days before eating.
For long-term storage, process in a hot water bath according to safe canning guidelines.