We've never made sushi, but I don't think it's terribly difficult. I think the tricky part is mastering the bamboo thingy that resembles a placemat.
We got the bamboo thingie. The ingredients of “California rolls” are cheap, so he can practice ... and if it turns out wrong, it’s krab-and-rice salad.
I make very plain sushis every now and then - hub and I love them, the bamboo roller things are very easy to master, just make the rice sort of sticky - often mochi or sticky rice is used, actually, and wet the very edge of the nori piece where it will stick on to itself, if you get my meaning.
I used to make them and sell them on trays, I would make the rice and then add a bit of soy sauce (IIRC), honey or sugar and rice vinegar mixed, stir it into the hot rice in a bowl, and mix it. Then when room temp I’d roll them up, with bits of stuff in the middle.
Since I’m a vegetarian, I’d put strips of carrot, daikon (white radish), strips of fried tofu and I can’t remember what else, it’s been a long time since I made them for sale. I’d also make what they called cone sushis (there is a Japanese word I suppose but I can’t remember) in which sushi rice is stuffed into little cones made of pressed fried tofu.
Maybe I’ll go make some rice for sushis right now. Yum - a good filling food that can be eaten cool, good for hot weather.