What to do:

Fill a medium pot with water until half full and bring it to a boil. Then, add potatoes and simmer it gently until tender (about 10 minutes).
Slice your radishes (optional), cucumber, and carrots into matchsticks, or you can use a peeler/mandoline slicer to slice these vegetables into thin pieces. If using a peeler/mandoline, slice cucumber and carrots into ribbons (long, thin pieces).
Once potatoes are cooked, use a slotted spoon to remove them and set aside. Once cooled down, cut potatoes into bite-sized pieces.
Assemble all ingredients in a large salad bowl or individual serving bowls.
Note: You can save the warm water to blanch other vegetables that you want to add into the salad. Substitute vegetables as you see fit. DIY and have fun!