Sweet and sour pineapple chicken

Ingredients

• 2 skinless, boneless chicken breasts , cut into cubes
• 2 tbsp Shoaxing cooking wine, sake or sherry
• 1 tsp salt
• 3 tbsp all-purpose flour
• 2 1/2 tbsp cornstarch , divided
• 1/3 cup vegetable oil
• 1 red bell pepper , cut into 1/2-in. bite-size pieces
• 3 tbsp packed brown sugar
• 2 tbsp white vinegar
• 2 tsp water
• 3 cups peeled chunks of pineapple
• 2 green onions , cut into 1-in. pieces