In a small bowl, add soy sauce, water, mirin, sesame oil, sesame seeds, ginger, garlic, brown sugar, and green onions and whisk to combine.
Place salmon in two 6 inch square pans or two 8 inch mini loaf pans and pour half of the marinade over the salmon (reserve half of the marinade for serving). Allow salmon to marinate for 30 minutes in the fridge.
Add 1 cup of water to the inner pot and place silicone trivet inside. Place the prepared pans inside, stacking them to form an X shape.
Secure the lid and turn the valve to seal position. Cook at high pressure for 8 minutes.
While the salmon is cooking, pour reserved marinade into a small saute pan over medium high heat on the stove top. Mix 1 tbsp of cornstarch with 1 tbsp of water and whisk to combine. Once the marinade comes to a simmer, slowly pour in the cornstarch slurry and whisk constantly until thickened, for about 2 minute and set aside.
When pressure cooking is complete, make a quick release.
Serve warm over rice and drizzle the teriyaki sauce over the dish. Garnish with green onion.