Make the glaze: In a small bowl, mix gochujang, mirin, soy sauce, sugar, sesame oil, and minced garlic until smooth.
Prepare the salmon: Place diced salmon in a large bowl. Add minced ginger and soy sauce. Let it sit for 5 minutes to marinate.
Cook the salmon:
Air Fryer Method: Spray the air fryer basket with olive oil. Place salmon evenly. Cook at 400°F for 5 minutes, shaking halfway. Brush glaze on salmon and cook for 1 more minute until cooked through and nicely browned.
Oven Method: Preheat oven to 425°F. Spread salmon on a sheet pan evenly. Bake for 8 minutes. Brush glaze on salmon and bake 2-3 minutes more until cooked through and glazed.
Assemble the bowl: Divide cooked rice and cucumber slices evenly into bowls. Top each with glazed salmon, scallions, and black sesame seeds. Serve with extra soy sauce if desired.