The only differences between setting up a laptop and a desktop come either prior to the Setup Assistant (connecting keyboard, mouse/trackpad, and for Minis and Mac Pros, the display) or after Setup Assistant is done (going into System Preferences to tweak things like mouse/trackpad, Dock behavior, sleep/wake, etc.).
I know, some of us like to write procedures that suit our particular logic, but Apple does a pretty fair job of walking folks through setup:
https://support.apple.com/HT205749
Since Setup Assistant runs only once and does offer options during the process (migrating data, in particular), you wouldn't necessarily be in a position to write a comprehensive guide without performing multiple erase/reinstalls in order to explore the various branches in the program.
If your friend is entirely new to Apple, will your guide include a primer on Apple ID and iCloud? Are you going to explain what Find My Mac is, and the reason for enabling Location Services if they do turn on Find My Mac? What about iCloud Keychain and FileVault? Will you discuss how owning an iPhone and/or iPad (and the settings on those devices) may affect the choices they make for the Mac in iCloud Preferences?
Or are you going to tell your friend to set it up in one particular way, based on your own preferences? If they choose a different option (accidentally or intentionally), will your instructions anticipate that, or will they have to call you for help?
As far as I'm concerned, the real "setup" options come after the Setup Assistant, when they're on the Mac desktop - tailoring their Mac to their needs. The more hand-holding we do for our friends and relatives during that process, the less self-reliant they will be forever after.