Terminal: how to use `at`?
The time spec for "10 minutes from now" is now +10 minutes. For example,

echo 'open ~' | at now +10 minutes


However, the at system is disabled by default in macOS, as mentioned in the at man page:

IMPLEMENTATION NOTES
     Note that at is implemented through the launchd(8) daemon periodically
     invoking atrun(8), which is disabled by default.  See atrun(8) for infor-
     mation about enabling atrun.


The atrun man page says that you need to run

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.atrun.plist