Wash cucumbers under cold water, trim the ends, and cut into spears, chips, or leave whole. Smaller cucumbers are best for pickling.
In a saucepan, combine water, vinegar, sugar, and pickling salt. Heat over medium, stirring until dissolved, then remove from heat before boiling.
Add smashed garlic, mustard seeds, red pepper flakes, dill seeds, and black peppercorns to the hot brine. Stir and let sit for a few minutes.
Layer cucumbers tightly in clean glass jars. Add garlic and spices evenly between jars.
Pour the hot brine over cucumbers, ensuring they're fully submerged. Leave a small gap at the top of the jar.
Seal jars tightly and let them cool to room temperature.
Once cooled, refrigerate the jars. Taste after 24 hours, but for the best flavor, wait 3-5 days.