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 I also think having a hardware wallet or what so called a tangible material like Trezor is the best choice or place to keep your bitcoin. It can have security and effective way of hold. But i do not consider it as mu only option in regards to my holding because i do keep bitcoin as a form of investments and trading. And when trading is a thing you must consider finding more easy to manage wallet just like application wallet and blockchain for easy access with the more widely used portion of your bitcoin.