Oven-Roasted Flounder with Bok Choy, Cilantro, and Lime

INGREDIENTS

• 1 scallion, thinly sliced
• 2 tablespoons unseasoned rice vinegar
• Kosher salt and freshly ground black pepper
• 1/4 cup coarsely chopped cilantro, plus small sprigs for garnish
• 1/4 cup fresh lime juice
• 4 4-ounce fillets flounder or other delicate white fish (up to 1/2" thick)
• 3 tablespoons reduced-sodium soy sauce
• 3 1/2 tablespoons vegetable oil, divided
• 1 pound baby bok choy (2-3 bunches), cut in half lengthwise
• 2 teaspoons finely minced peeled ginger
• 1/2 cup sake or dry white wine