Sanitize canning jars and lids according to manufacturer’s instructions for sterilized jars. Keep jars hot. Read the Ball book on this. It's important.
Wash cucumbers. Cut off a bit from the blossom end and discard. Leave cucumbers whole, cut into spears, or slice.
In a large non-reactive pot, combine the water, vinegar, and pickling salt. (Don't use an aluminum pan.) Bring to a boil. Remove from heat.
In the bottom of each hot jar, place a head of fresh dill, a couple cloves of smashed garlic, a 1/4 teaspoon red pepper flakes, and 2 to 3 peppercorns. Pack the cucumbers snugly into the jars, leaving 1/2-inch headspace. Pour the hot pickling liquid into the packed jars, leaving 1/2-inch headspace. Remove air bubbles, wipe rim and cap each jar as it is filled.
Process quart jars for 15 minutes, in a boiling water bath canner. Remove the jars and place a few inches apart on a towel on the counter. Leave jars alone to cool at room temperature overnight. Wipe the tops, remove the bands and check to see that the lids are tight. If you can't pry them off with your fingers, you're good. Be careful, though, I once got a pickle shower when a lid didn't seal properly. Refrigerate any that don't seal and eat those up within a few weeks.
Label and store in a cool place. Their flavor will develop over time.
Nutritional values are approximate and are based on 1 quart of the recipe (makes 7 total). Refrigerate leftovers promptly and use within 4 days.