Slice cucumbers as thinly as possible (with mandoline or by hand). Place a colander either in a clean sink or over a bowl. Layer the cucumbers in a single(ish) layer in the colander, or on paper towels or clean kitchen linen, and sprinkle with salt. Let sweat for at least 30 minutes to release excess liquid.
Use mandoline to slice 1/2 of a large white onion in thin half circles and add to a medium sized bowl.
Optional: Heat a small saute pan over medium heat. Add sesame seeds and toast for 1 -2 minutes stirring constantly so they don't burn.
In a small bowl add rice vinegar, sesame oil, ginger, oyster sauce, and dill and mix well.
After 30 minutes of sweating, transfer cucumbers to a colander and rinse off excess salt and liquid. Shake off excess water and then gently press with paper towels or a clean dry kitchen linen to remove excess liquid.
Add cucumbers to the bowl with the onions. Pour over vinegar dressing and mix well. Sprinkle with sesame seeds. Cover and refrigerate for about 10 minutes and then serve and enjoy!