Mentor Group Gold
And no, the most secure way is to do it manually in a paper where it never touches something that is connected to internet.
Actually that's all I did in the end. I kept a paper copy with clear instructions in a safe. Then kept another paper copy at another location and kept with me a ledger on a keyring. More important at the time was ensuring my next of kin could easily get to the crypto in future in case I got hit by a bus. Don't need to anyone trying to unlock the 36 chambers to get to the crypto.