Wrap your sushi mat in plastic wrap so that the rice does not stick to the bamboo.
Put the ½ seaweed sheet on the mat with the rough side up.
Lay ¾ cup rice across the entire roll (you may not need to use all the rice), then flip the seaweed over so the smooth side is showing.
Cut ½ an avocado into thin strips and place the strips lengthwise in the center of the seaweed.
Cut the crab stick into thinner slices if needed. Place them on the seaweed next to the avocado.
Add a few slices of cucumber on top of the avocado and crab, lengthwise.
Place your thumbs under the sushi mat. Then lift the edge of the mat closest to your belly up and over the filling in the center.
Use your hands to press the length of the log, making sure that all of the sushi ingredients are staying together. Continue lifting and rolling the edge of the sushi mat until the sushi is in one roll. Gently press with your hands again to make sure that the rice on the outside edge is sticking together. If you need visual instructions for this process, I enjoyed watching this video.
Lay the thinly sliced fish and fruits over the top of the sushi roll with the edges slightly overlapping. Go in this order: tuna, salmon, mango, avocado, repeat.
Lay plastic wrap over the sushi roll and place your mat on top. Squeeze the mat on top of the roll so that the toppings stick to the rice.
Remove the plastic and use a knife to cut the sushi into 8 pieces. Serve and enjoy!