Sun-drying: drying something by exposure to sunlight (and air), commonly used for laundry, bedding, fish, vegetables, and herbs.
雨上がりなので布団を天日干しにした。
Since the rain stopped, I put the futon out in the sun to dry.
干物は魚を塩で処理してから天日干しにして作る。
Dried fish are made by salting the fish and then sun-drying them.
ハーブは風通しの良い場所で天日干しすると香りがよく残る。
Herbs retain their aroma well when sun-dried in a well-ventilated spot.