Any recipes you've used as a baseline?
I've been winging it based on an amalgam of online recipes. It involves lots of steps but it's pretty easy to assemble.
For most the vegetables, eg. carrots, bell peppers, zucchini, I slice/julienne/chop them as needed and saute individually in a little grape seed oil, then toss with a little soy, sugar and sesame oil. Same procedure for spinach and soy bean sprouts but I blanch them rather than saute. I've been using flank/skirt/hanger steak and I don't marinate it but I salt it/sear it over high heat, then toss with soy/sugar/sesame oil. I've been using sushi rice soaked for a few hours, then cooked in the rice cooker.
To assemble, I heat the dolsots with a little vegetable oil, then add sushi rice and heat some more, then add the toppings +/- a fried egg and toss with ssamjang. For the ssamjang, I've been using a doenjang/gochujang mix (I make a base recipe with mostly doenjang, then add extra gochujang to mine--I like it spicy) with a little rice vinegar, crushed garlic, sugar or honey, sesame oil, +/- minced scallions. I've been making the ssamjang and vegetables a day in advance so that it's a pretty easy weeknight dinner to sear the steak and assemble.
I don't make any claims about authenticity but it tastes pretty good. I haven't yet tried adding fernbrake or bellflower.
I've also made it in a cast iron pan and that works nicely too
It's a work in progress...