Wash the cucumbers thoroughly and trim a thin slice from both ends.
Cut the cucumbers into spears, rounds, or sandwich slices.
Place the fresh dill, garlic, mustard seeds, and black peppercorns in the bottom of a clean 1-quart glass jar.
Pack the cucumber pieces firmly but gently into the jar.
Combine the water, white vinegar, kosher salt, and sugar in a small saucepan.
Heat over medium heat while stirring until the salt and sugar completely dissolve.
Remove the brine from the heat and allow it to cool for several minutes.
Pour the brine over the cucumbers until they are completely submerged.
Gently tap the jar or use a clean utensil to release trapped air bubbles.
Allow the jar to cool to room temperature if necessary.
Cover tightly and refrigerate for at least 24 hours.
For stronger flavor, refrigerate for 48–72 hours before serving.
Keep refrigerated and enjoy within approximately 3–4 weeks.