How do you make homemade flux?

As a finance and cryptocurrency professional, I don't typically dabble in DIY electronics projects, but I'm curious to know about the process of making homemade flux. Could you elaborate on the steps required? I understand flux is a chemical agent used in soldering to remove oxides and impurities, ensuring a strong bond between metal surfaces. What ingredients are typically used in a homemade flux recipe? Are there any safety considerations I should be aware of? Additionally, how does the homemade flux compare to commercially available options in terms of effectiveness and cost?