Add the gochujang, rice vinegar, soy sauce, crushed garlic, and minced ginger to a shallow dish. Whisk until combined into a smooth sauce.
Add the salmon cubes and gently toss until thoroughly coated in the gochujang mixture.
Prepare the sticky rice according to the package directions. Keep it warm while you cook the salmon.
Heat the vegetable oil in a non-stick frying pan over high heat.
Once the oil is hot and shimmering, carefully add the marinated salmon pieces.
Turn the salmon bites shortly after adding them to the pan so they cook evenly without burning the sauce.
Pour the remaining gochujang mixture from the dish into the pan. Gently stir and cook until the salmon is just cooked through.
Divide the warm sticky rice between serving bowls.
Arrange the spicy salmon, cucumber, and chopped kimchi over the rice.
Spoon any remaining sauce from the pan over your Spicy Salmon Rice Bowls and finish with toasted sesame seeds, if desired.