Set your oven to 425°F before you do anything else. This gives it enough time to fully preheat while you're prepping the salmon and cucumbers. A hot oven is what gives the salmon that slightly caramelized edge without drying out the inside.
Remove the skin from the salmon fillet and cut the flesh into cubes roughly one inch thick. Cutting it evenly helps the pieces cook at the same rate, so you won't end up with some cubes overdone while others are underdone. Set the cubes aside in a mixing bowl.
Add the soy sauce, sriracha, rice vinegar, sesame oil, and ginger powder directly into the bowl with the salmon cubes. Toss everything together gently so each piece gets coated in the marinade. Let it sit for just a few minutes while you prep the rest, since salmon doesn't need long to soak up flavor.
Spread the marinated salmon cubes onto your baking sheet in a single layer, making sure they aren't crowded together. Bake for 10 to 12 minutes, until the salmon flakes easily with a fork. Keep an eye on it near the end so it doesn't overcook and dry out.
While the salmon bakes, combine the sliced cucumber, rice vinegar, sesame oil, soy sauce, and sesame seeds in a separate bowl. Toss well so the dressing coats every slice evenly. Let this sit and marinate on the counter while the salmon finishes cooking.
Start each bowl with a scoop of warm white rice as the base. Add the baked salmon, a portion of the cucumber salad, and the grated carrots on top. Finish with sliced green onions, extra sesame seeds, and a drizzle of the leftover cucumber dressing for extra flavor.