Missing description on building a bootable recovery disk

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I purchased the first edition of mac OS Sierra. I want to make an emergency boot disk on a flash drive so if something goes wrong as it did on my husband's computer running Sierra, I can reinstall the OS. On p 802 it talks about "build yourself a bootable recovery disk as described on P 799." On p 799 there is no description on how to do this. So, is there this description somewhere else in the book?