In a medium bowl, whisk together the soy sauce, brown sugar, sesame oil, minced garlic, and grated ginger. Add gochujang if using. Add the thinly sliced steak and toss to fully coat. Cover and refrigerate for at least 30 minutes or up to 4 hours.

While the steak marinates, prepare your toppings. Cook the rice, shred the carrots, slice the cucumbers, and chop the green onions.

Heat a large skillet or wok over high heat. Add a tablespoon of neutral oil. Once hot, add the marinated steak in a single layer, working in batches if needed to avoid overcrowding the pan.

Cook the steak for 1-2 minutes per side until well-browned and cooked through. The thin slices will cook very quickly.

To assemble the bowls, divide the cooked rice among four bowls. Top with the cooked steak, and arrange the carrots, cucumbers, and kimchi around the sides. Garnish with green onions and sesame seeds before serving.