Add cucumber slices to a large mason jar or glass container along with coriander seed, mustard seed, and dill. Set aside.
To a small saucepan add distilled white vinegar, sugar, and salt. Bring to a simmer over medium heat and stir to fully dissolve salt and sugar. Taste and adjust flavor as needed, adding more salt or sugar to taste.
Let the brine cool in the refrigerator for at least 30 minutes to 1 hour. Once cooled, pour the brine over the cucumbers until your glass container is full. Ensure the cucumbers are fully submerged. If needed, add more vinegar or a little water to cover.
Seal well and shake to combine. Then refrigerate for at least 1 hour. The flavors will deepen and intensify the longer it marinates. Best flavor is achieved after 24 hours.
Will keep in the refrigerator for 2-3 weeks (sometimes longer). Not freezer friendly.