Cut tofu and spam into similar-sized pieces. Slice onion and green onion thinly.

Layer sliced onion at the bottom of a pot.

Alternate layers of tofu and spam on top of the onion.

Add sliced green onion on top.

Mix red pepper flakes, soy sauce, sugar, minced garlic, sesame oil, and fish sauce in a bowl to create the seasoning sauce.

Pour the seasoning sauce over the layered ingredients and add water until slightly submerged. Turn on the heat.

Once boiling, spread the seasoning sauce evenly.

Simmer on low heat for about 10 minutes or until the stew thickens. Adjust time based on desired consistency.