Mash avocado using a fork in a small bowl; add lemon juice and salt and pepper to taste.
Place ring form in the center of plate (or bowl: see notes)
Add ingredients in layers **(see notes)
Carefully press down with the pusher. Some moisture might come out at the bottom around the ring - dab it with the paper towel.
Continue applying light pressure to the pusher as you pull the ring out. Run a knife between the pusher and the top layer (very close to the pusher) to release any stuck-on pieces.
Mix any remaining pieces and place on top.
Serve with sesame seeds and soy sauce, if desired.