Wash the cucumbers thoroughly and trim off both ends.

In a medium saucepan, combine water, vinegar, and kosher salt. Heat over medium heat until the salt has dissolved, then remove from the heat and let the brine cool slightly.

Prepare 3 pint-sized jars by washing them with hot water and ensuring they are clean and dry.

Place 2 smashed garlic cloves, 2 sprigs of fresh dill, 1 teaspoon black peppercorns, 1 teaspoon mustard seeds, and a pinch of red pepper flakes (if using) into each jar.

Pack the cucumbers into the jars tightly, ensuring there is minimal empty space but not crushing them.

Pour the cooled brine into each jar, covering the cucumbers completely. Leave about 1/2 inch of headspace at the top of the jar.

Seal the jars tightly with lids and refrigerate them. Allow the pickles to sit for at least 24 hours before eating for the flavors to develop, but they are best after 2-3 days.