Where works best for a solo stay?
Myeongdong is the easiest place to start when this is your first trip and you want central sightseeing, food and simple daily routes. Hongdae suits a more active solo trip with cafés, nightlife and direct AREX access. Seoul Station and Mapo / Gongdeok are less about atmosphere and more about making airport transfers, luggage and arrival days easier.
Insadong is a quieter central alternative for travelers drawn to palaces and older neighborhoods, while Gangnam makes more sense when several plans are already south of the Han River.