river in Shandong, space inside
祊 is a rare kanji with two disconnected meanings: a specific river name in Shandong, and an interior space or room. There is no clear conceptual link between these senses, so treat them as separate uses.
The exact historical development of 祊 is uncertain. It combines 示 (altar, spirit) with 方, but the original semantic and phonetic roles are unclear.
The left side 示 suggests something related to ritual or spirit, and the right side 方 can mean direction or method. Imagine a sacred space marked off by directional signs, creating an interior room for ceremonies.
For ホウ, picture a sacred hall (ホウ sounds like 'hall') where rituals are performed inside the space marked by 示 and 方.