Method Seven: Use Cold Wallet
Cold wallet are a bit expensive, as your crypto assets grow the need to keep your fund well secure offline becomes necessary. A cold wallet which is also known as a hardware wallet is an offline wallet that is not connected to the internet. it is like a flash drive that you can store your crypto assets on. Popular examples are Ledger Nano and Trezor Wallet
Just to add, paper wallets are cold wallets too, and they cost almost nothing to produce. You can also use software wallets like Electrum or Bitcoin Core as de facto hardware wallets by setting them up on an air gapped computer or a flash drive with a bootable operating system.