Peel and julienne radish into thin matchsticks. Place radish in a large bowl, toss with salt . Leave salted radish in bowl to draw out liquid for 10 minutes, up to 30 minutes.
Drain liquid from radish, gently pressing on radish or squeezing with hands. Discard salty liquid.
Add garlic, green onions, gochgaru, and vinegar to the radishes. Mix the seasonings with the radish until everything is evenly distributed.
If you are eating Spicy Korean Radish Salad immediatemyl, transfer to a serving bowl, garnish with toasted sesame seeds.
If you are going to store the Spicy Korean Radish Salad to eat within the next couple of days, transfer seasoned radishes to a large glass container with a tight-fitting lid like a glass jar. Garnich with toasted sesame seeds just before serving.