Prepare the cucumbers by slicing them how you like, spears or rounds both work great. Place them in a glass mason jar or a bowl.

In a medium pan, add the water, vinegar, sugar, salt, peppercorns, whole mustard seed, and red pepper flakes. Stir to combine.

Over medium-high heat, bring the mixture to a boil and boil for one minute. Remove from the heat and pour the mixture over the prepared cucumbers.

Let the cucumbers and vinegar mixture rest in the fridge for at least 30 minutes (though overnight is great, too) before enjoying.

Keep pickles in the fridge, submerged in the brine, for up to a week.