Rinse the oysters gently in a bowl of water, changing the water 2–3 times. Drain and pat dry with a paper towel.

Slice the green onion thinly at an angle and slice the garlic, removing the core.

Spread the green onion in a microwave-safe dish, place the oysters on top without overlapping, and add the garlic slices. Drizzle sake over the oysters.

Cover loosely with plastic wrap and microwave at 600W for 3–4 minutes until the oysters are cooked through.