Inspect three pint-sized jars for cracks and rings for rust, discarding any defective ones. Wash the glass jars and lids in hot, soapy water, then rinse them well to remove all soap residue.
Fill a large stockpot halfway with water. Bring to a boil and carefully lower the jars into the boiling water with canning tongs (make sure they're about 2 inches apart). Add enough boiling water to cover the jars by at least an inch. Heat to a rolling boil, cover, reduce heat, and let them boil for about 10 minutes.
Remove the jars with canning tongs from the pot and let them cool enough to handle on a kitchen towel several inches apart. To sterilize the lids, place lids in a large bowl and pour boiling water over them.
Bring the water, vinegar, salt, sugar, coriander seeds, red pepper flakes, and black peppercorn to a boil in a saucepan over medium-high heat. Simmer for 2-3 minutes or until the salt and sugar dissolve.
Rinse the okra and pat dry. Trim just the stems to around ¼ inch with a small knife, avoiding cutting the pods.
Divide okra evenly between the hot, sterilized jars, filling the jar as much as possible with the okra pods top down. Fill in gaps with additional okra top side up. Add a garlic clove or two, chili peppers (if using), and a sprig of dill to each jar.
Then, pour the hot brine in, ensuring the okra is entirely submerged. Run a small spatula or spoon around the inside of the jars, gently shifting everything slightly to release air bubbles.
Wipe the rim of each jar with a clean cloth and screw the lids on tight.