Bring a small pot of water to a boil, add the egg, and cook for 6.5 minutes for a jammy yolk, then immediately transfer to an ice bath.
In a small bowl, toss the sliced cucumbers with rice vinegar and a pinch of sea salt, then set aside to quick-pickle.
Heat a large skillet over medium-high heat and brown the ground beef until fully cooked, draining any excess fat from the pan.
Stir in the minced garlic, grated ginger, coconut aminos, and red pepper flakes, simmering for 2 minutes until the sauce coats the beef.
Push the beef to one side of the skillet and quickly wilt the fresh spinach with a splash of water for 1 minute.
Assemble the bowl by placing the cooked brown rice at the base, followed by the bulgogi beef, wilted spinach, and pickled cucumbers.
Peel and halve the soft-boiled egg, place it on top, and drizzle the entire bowl with toasted sesame oil.
Garnish with sliced green onions and sesame seeds before serving.