only a properly created cold storage or a trusted hardware wallet.
you can search for some hardware wallets if you are not tech savvy or don't want to bother learning how tos and if you are willing to pay. things such as Trezor or Ledger nano would work.

or you can learn more about cold storage and do it yourself easily. like creating a paper wallet with tools such as https://github.com/pointbiz/bitaddress.org or make a Trezor like cold storage on your USB disk yourself

https://en.bitcoin.it/wiki/Cold_storage