Preparation

1. Cut each cucumber in half lengthwise. Slide a narrow spoon through the seedy portion to scoop out the seeds. Place cucumbers cut side down, thinly slice crosswise and transfer to a large bowl. Add salt, sugar, and vinegar and toss to coat.
2. In a small skillet, heat the sesame oil over moderately low heat. Add ginger, garlic, and red pepper flakes and cook until fragrant, about 1 minute. Remove from heat and allow to cool. Pour spiced oil through a strainer and onto the cucumbers. Discard spices.
3. Toss cucumbers to coat and marinate for at least 3 hours or up to 5 days, stirring occasionally.