you should use metal ones with many backups in case of a fire and on the signer use an additional password. you could also use offline digital ones but you need to understand exactly what you are doing. safer for most people are metal plates. you could make a backup with washers which you stamp with four letters each and put together with a screw.
Discussion
Are there any guides?
amazon has such plates. does not cost much. some come with a stamp tool and a guide. you can use paper first and draw it by hand, it will work too. there are many videos on youtube. or you can print it if you have a printer
here is a guide how to back it up on metal:
the qr on paper you can do it with a marker. there is no need to laminate because you have the backup and you can make a new one any time.
put the backup on metal plates like the one i sent. make 2 or 3 backups in case anything gets lost.