Is it better to sell salam or to continue with agency in buying and drying fish for a commission, along with returning any remaining money?

The contracts of agency (wakalah) and forward sale (salam) are permissible, provided their conditions are met. The transactor chooses the easier of the two and the one further removed from sin. The agent (wakil) is not liable unless there is transgression or negligence. Therefore, the forward sale (salam) contract is the most suitable if its conditions are met.