Prepare all ingredients as described above.
In a very large bowl, combine bok choy, carrots, cucumber, cabbage, onion, apple, salt, and enough spring water to cover. Spring water is important – avoid tap water if at all possible. You don't want fluoride in your kimchi.
For the bowl of kimchi ingredients, find a plate or something flat that you can use to compress the mixture. Place something heavy and waterproof on top of the flat surface to weigh down the ingredients and keep them submerged in the salt bath. This allows the ingredients to be cured completely before beginning the fermenting stage.
Allow this mixture to sit for 8-12 hours at room temperature.
In the meantime, you can create the kimchi paste.
Combine the red pepper powder and just enough warm water to create a paste.
In a food processor, blend apple, red pepper powder, garlic, and onion into a puree. Add the red pepper paste to the food processor and blend until well combined.
Once the vegetables have cured for 8-12 hours, drain the salt water into a bowl or jar and set aside.
Add the paste mixture that you created and mix into the vegetables until well combined.
Transfer the kimchi into glass jars and pour in enough of the excess water to cover the mixture in each jar. Seal tightly.
Store at room temperature for 24-48 hours, then refrigerate. The kimchi should stay good for 3-4 weeks in the refrigerator.