1. Grilled salmon with salty flavour is a typical Japanese way of grilling salmon. Before grilling, sprinkle ½ teaspoon of salt (for this size) all over the salmon and leave it for 15 minutes. Then grill it just like grilling any fish.
2. Use short grain rice (preferable) or medium grain rice as the grains need to have starch to stick to each other. Please cook the rice in the way the Japanese do, ie. absorption method. You can visit my post How to Cook Rice The Japanese Way for that.
3. The amount of salt required varies depending on how salty you like the outside of the onigiri to be. You just need to try and adjust.
4. Yaki nori (焼き海苔) is roasted seaweed sheet. A full size yaki nori sheet is 19cm x 21cm (7½” x 8¼”). Cut in the centre vertically along the longer side.
You can make the size of yaki nori sheet much smaller per onigiri if you like as there are no rules to it. You don’t even have to have yaki nori but I find that it is easier to eat onigiri with yaki nori because otherwise the rice will stick to your hands.
5. Check to make sure the salmon is in the middle of the rice ball. If you can see a piece of salmon sticking out or placed very close to the surface of the onigiri, take some rice from the corner of the triangle and cover the salmon.
6. Insufficient firmness will make the rice ball fall apart when picked up or while eating.
7. I usually place 4 mounds of rice on the cutting board at once and do each step for all of them. This seems to be most efficient.