It is really simple:
-Create an offline wallet with Bitcoin Core and encrypt it (I recommend using PGP on top of the original encryption for privacy reasons)
-Backup this encrypted wallet.dat file anywhere you want. You can put it on several harddisks, usb sticks. You can send it attached to several email addresses.
I keep most of my coins on encrypted wallet.dat, but it's not possible to do day-to-day spending this way. I just use them for coins I don't expect to move for months or years.
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I don't think, that a 'day-to-day-wallet' needs to be secured in an offline wallet in most of the cases.