Start with the pickle. Cut the carrots julienne. Place in the pickle press, along with the salt, chili flakes and black sesame. Knead the salt well through the carrots, using your hands. Put the lid on the pickle press and let it ferment for 1 to 4 hours.
Boil the sushi rice in a pan with plenty of boiling water for 15-20 minutes. Drain and return to the pan.
Add the genmai su and toss gently. Let cool to room temperature.
Place a sheet of nori shiny side down on your sushi mat. Cover two-thirds of the sheet with a layer of sushi rice. Leave the top part free horizontally.
Slice the avocado. Place in a horizontal line on the rice, in the middle. Do the same with the sushi ginger and a handful of pickled carrot.
Roll the sushi, including the sushi mat, away from you. If necessary, grab the bottom of the roll and push the sides a little inward, so that your roll is nice and tight. Continue to roll until only the top piece of the sheet is left. Moisten this with some water and seal the roll.
Cut the roll in half with a sharp knife. Cut the rest into slices.
Dip in some ume paste and / or shoyu or tamari.
You're left with carrot salad. This is necessary, because if you use less carrot in the pickle press, there is not enough pressure and the vegetables will ferment less well. Don't have a pickle press? Then let the carrot rest in some extra genmai su, a few pinches of salt, the chili flakes and the sesame seeds.