Boil the sushi rice, follow the instructions on the package for the ratio rice to water and the duration to cook it. Once the rice is boiled, transfer it to a bowl and let cool for 24 hours at 4 degrees celsius (for the resistant starch).
Prepare your work area. Mix the sushi rice with 6 tbsp rice vinegar and 1 tsp salt. Mix thoroughly, to cover all the rice with a small layer of vinegar and salt. Set aside.
Make sure you have all your ingredients within hand reach. Drain the canned tuna and mix it with 1 tbsp mayonnaise for the tuna filling. Slice the salmon, other fish you might have, avocado and cucumber and all other ingredients you have into small strips.
Spread the sesame seeds or tobikko on a large plate.
Place a bowl of water near you.
Get a nori sheet and place on top of the bamboo mat. Wet your fingers/hands and get some rice from the bowl (wet fingers make the rice stick less to your hands). Spread the rice in a thin layer over 3/4 of the bamboo sheet. At the bottom of the sheet, place the ingredients you want in the sushi over the complete width of the bottom of the sheet on the rice and start rolling from the bottom. Make sure the roll is tight, and use the bamboo mat to keep it tight and to spread the pressure over the roll equally.
Keep rolling until you reach the top, where there is no rice. Spread a little bit of water on the nori sheet to make it sticky, and roll to the end of your sheet.
Get the sushi roll from the bamboo sheet onto a cutting board and cut the sushi into pieces with the super sharp knife.
For the temaki (the sushi 'bags'): cut the nori sheet in half. Place the rice and the desired fillings into the top left corner of the nori sheet and keep the filling about 1 cm from the bottom of the nori sheet. Start rolling from the corner to make a cone.
For the inside out rolls (these are more of a hassle, prepare these last because your bamboo mat will be dirty after this): Make sure your fingers/hands are wet. Place the rice directly on the bamboo mat, and spread evenly until the whole of the mat is covered. Place a nori sheet on top of the rice, make sure the top 2-3 cm of the rice remains uncovered with the nori. Place your desired fillings on top of the nori at the bottom of your mat and start rolling. Keep the roll tight and roll all the way up. Carefully separate the sushi roll from the bamboo sheet (this may be a little sticky) and place the roll on the plate with the sesame seeds or tobikko topping. Roll until it's completely covered in the topping.
Transfer your roll onto a cutting board, and cut the sushi into pieces with the super sharp knife.
Once you're done making all the desired rolls and have beautifully placed them onto a serving tray. Add some soy sauce and wasabi in a bowl to dip the sushi into. Yum! Enjoy.