The idea is to have a full bitcoin node installed in a decent system like a linux partition that you don't use for much other than to have the full node so you lower the surface attack (and not use Electrum because it's not ideal, some consider HD wallets unsafe).

Then, you would have something that's completely sealed like an airgapped laptop, and you would do the actual signature there, then you save this information in an USB or something and then relay it into the network with your full node.

The problem is I dont really know how this method works. How do you make the offline transaction, then pass it on the full node linux partition safely?