Heat 1 Tbsp. oil in a medium skillet over medium-high. Add scallions, season with salt, and cook, turning occasionally, until scallions are charred in spots and slightly softened, about 1 minute. Transfer to a plate. Wipe out skillet. Heat 2 Tbsp. oil in same skillet over medium-high. Season fish with salt and cook, skin side down, until very crisp, about 4 minutes. Flip fish, add green juice and scallions, and cook until fish is just cooked through, about 2 minutes more. Taste and season with salt, if needed. Divide fish and scallions among bowls; top with green sauce. Drizzle with oil and serve.