Press cooked sushi rice (recipe here) onto your desired platter.
Use a mandolin slicer or sharp knife to chop carrot and cucumber into thin slices. If using a mandolin slicer, be extremely careful. A mandolin slicer glove costs just a few dollars and is way easier to use than the attachment that comes with the slicer itself.
Spread chopped vegetables onto sushi rice.
Slice salmon and tuna filets into 1/4 inch thick slices. Layer on sushi rice.
Slice avocado and add to pizza.
Use a scissors or cooking sheers to cut nori into thin 1-inch strips. Layer onto pizza. Top with additional sliced vegetables, sushi seasoning, and sesame seeds.