1 ½ pound 4-inch pickling cucumbers, stems removed and cut into quarters ⅓ cup thinly sliced halved red onion 6 sprigs fresh dill 6 cloves garlic, thinly sliced 2 teaspoon coriander seeds 2 teaspoon whole black peppercorns 2 teaspoon celery seeds 1 teaspoon mustard seeds ½ teaspoon crushed red pepper (optional) 1 ¾ cup water 1 ⅓ cup white vinegar 1 tablespoon sugar 1 tablespoon salt