Brush the salmon fillets with mirin and toasted sesame oil, and season with sea salt. Place salmon in refrigerator for 15 minutes.
Preheat oven to 375F. Layer a baking pan with foil, and lightly grease with vegetable oil. Place salmon fillets on foil. Bake for 15-20 minutes – depending on the thickness of the salmon.
While salmon is in oven, combine all the ingredients for the bibimbap sauce in a bowl. Whisk well to combine. Taste, and adjust any seasonings if desired. Set aside.
Heat oil in a frying pan over medium fire. Add in carrots and a pinch of sea salt, and stir-fry for about 2-3 minutes – or until crisp-tender. Set aside.
If adding in bean sprouts, use the same pan, and repeat the same cooking process. Set aside.
Again, repeat the same step with the spinach, but cook it very quickly until just wilted. Remove from heat, and gently stir in a teaspoon of soy sauce, a few drops of toasted sesame oil, and a sprinkle of toasted sesame seeds. Set aside.
Once salmon is cooked, flake the salmon with a fork.
To assemble, first place the cooked rice into each serving bowl. Arrange salmon, vegetables, and any additions (such as kimchi) nicely in a circle. Garnish with scallions. Serve immediately with the sauce on the side. When ready to eat, pour the sauce in, toss to mix well, and enjoy!