Decide what you want to replace: seaweed taste (nori), sesame crunch (sesame salt/seeds), or umami (bonito flakes).
Start with a 1:1 swap for toppings (same amount as the furikake you’d use).
If your substitute is less salty than furikake, add a tiny pinch more salt or sesame salt; if it’s saltier, use a little less than 1:1.
For crunch: keep flakes dry; if using a wet mix (like thinned soy sauce), toss right before serving.
Taste on the rice first, then adjust once—small changes match furikake’s layered flavor without overpowering.