What is the safest way to store USDT?

Could you please elaborate on the safest method for storing USDT? I'm interested in understanding the various options available and the relative risks associated with each. Specifically, I'd like to know about the security features and reliability of hardware wallets, software wallets, and custodial services. Additionally, are there any specific steps or best practices that one should follow to ensure the utmost safety of their USDT holdings? Your insights would be greatly appreciated.