Trim your fillet so that the edges are even.
Slice the fish with a sharp knife horizontally. You can watch a YouTube video on how to slice sashimi fish. Put slices of fish aside.
Layer overlapping cucumber slices on a plate. Fold over your fish slices on top of cucumber. Layer them like fallen dominoes.
Drizzle ponzu on top of fish. Add decorative slices of scallions. Be creative! Sprinkle top of everything with furikake.