When describing someone's position, there are various synonyms for the phrase "sitting on" that can be used. These include "perched on," "resting on," "balanced on," "seated upon," "occupying," "lying on," "leaning against," "supported by," and "propped up on." These phrases can be used to provide a more vivid description of someone's posture or position, especially in creative writing or descriptive passages. Alternating between these phrases and using them contextually can help writers add depth and variation to their writing, making it more engaging and intriguing for their readers.