Its not the safest way because ledger often has bugs in their wallet. Also there is no good enough decentralized exchange yet. A few years later maybe this would be the safest way. There is always a risk when you do anything on the internet. Sometimes being too precautious may lead you to doing something much stupid. Just use the normal exchanges like binance or something,and use whatever hardware wallet you have. If you are in no hurry to sell,use a paper wallet.