5 cups cucumbers, thinly sliced (and quartered if using large cucumbers)
1 cup carrots, thinly sliced
½ an onion, thinly sliced
2 ½ tsp salt
3 tbsp gochugaru (Korean red pepper powder)
3 tbsp rice vinegar
3 tbsp soy sauce
1 tbsp sesame oil
2 cloves garlic, minced
Optional: sesame seeds for garnish
Toss cucumbers, carrots, and onion in a large bowl until loosely mixed, then sprinkle with salt, toss again, and let stand for 20 min. While vegetables are soaking, combine gochugaru, vinegar, soy sauce, sesame oil, and garlic in a small bowl to form a wet paste and set aside. When the vegetables are done soaking, drain them in a large strainer, rinse in cold water, drain again, and pat with a clean kitchen or paper towel until they're somewhere between damp and dry, then return to bowl. Stir in the paste until everything's evenly coated, transfer to a large jar (I use an 8 cup mason jar, but you could get away with a little smaller), leave out on the counter overnight to age, and then refrigerate, garnishing with optional sesame seeds when served.
Notes
This is my adaptation of an All Ways Delicious recipe available here: https://allwaysdelicious.com/cucumber-kimchi/
I like to use small cucumbers and baby carrots, but larger vegetables are fine, just make sure to cut them into bite-sized pieces.
As for aging on the counter: I've only ever aged this type of kimchi for 1 day, and other types of kimchi for a max of 3 days, before refrigerating; do your own research if you want to age it longer and remember kimchi still ages (just far slower) in the fridge.