Preheat the oven to 350 degrees F (175 degrees C).

Melt butter in a microwave-safe bowl in the microwave. Crush ramen noodles into small pieces; stir crushed noodles, almonds, and sesame seeds into melted butter. Spread mixture onto a baking sheet.

Bake in the preheated oven until golden brown and crunchy, 8 to 10 minutes; allow to cool completely.

Toss together coleslaw mix and green onion in a large serving bowl.

Make dressing: Whisk together oil, sugar, vinegar, soy sauce, and reserved seasoning packets in a separate bowl until well combined.

Stir cooled noodle mixture into dressing. Pour dressing over coleslaw-onion mixture; toss to coat.