Contrary to what most people think, sushi is really easy to make. I made a batch with my mum, and all you need is sushi rice, seaweed, rice vinegar, sugar and whatever filling you want!
Ours was super yum, except we could have added more sugar to the vinegar-sugar mix (we reduced the sugar quantity, thinking it would be too much).
I made an egg filling by cracking an egg into a pan, adding salt and pepper, and breaking it up with a spatula as it fried to create crispy scrambled egg. (cook it for less time for a softer egg, or make an omelette and either slice it into strips or place it whole). The cucumber filling is just sliced cucumber soaked in vinegar. There are loads of other fillings, such as mushrooms and seafood.
Essentially, you just follow the cooking instructions on the packet of sushi rice (remember to wash the rice a few times!), assemble the sushi, wrap in it clingfilm, chill it and slice it up! Serve with chili or soy sauce.
This is just to show you how to lay out the sushi for rolling. You don't need a bamboo mat-- we make it just fine without one. Spread out your rice but leave a gap at the end because the rice will spread as you roll. Place a strip of filling so that the seaweed and rice wrap around it nicely. Photo from Barefoot Floor