Well if you've understood how the entire thing works, then it's easy. I mean, if you do know that you have to keep your private keys safe in order to prove you are the owner of your addresses then you're okay.
There are plenty ways of generating private keys and then getting the addresses, but the greatest and most secure option for a beginner is a hardware wallet like those you mentioned. (Nano Ledger, Trezor etc)
If you feel that you don't need a hardware wallet then,
electrum does fine.
Is there another more definitive, secure method of accumulating BTC for long term holding?
As I said before, if you understand the way it works you don't have to worry. For example, if you find out that you can access thousands of addresses by only writing down 12 words, then you only need that paper for the rest of your HODLing.
You should never keep your funds on custodian wallets like blockchain.com and consider it as "cold storage".