I am absolutely loving learning from Kenji's book, The Wok. It is an awesome cookbook, and this is a great recipe. The kimchi adds lots of fun flavor. We were unable to find pork belly, so used country style ribs instead. I marinated the pork for longer than the recipe instructed because country style ribs are tougher than pork belly. The pork came out succulent and flavorful. Given the tasty end results, and how cheap country style ribs are, I have no regrets about the switch.
Something useful to know about stir-frys is that in my experience, a stir-fry recipe with one pound of meat will comfortably feed two people dinner. Jackson and I usually make double batches of stir-fry recipes, so that they provide two nights of dinner. When you double a stir-fry, you need to make it in more batches, since woks don't work as they're supposed to when over-crowded. Given how quickly everything cooks in a wok, the increased number of batches is not too bothersome.