We use dockutil to create the dock, along with a cached policy runs at login to create a default dock (at every login). However, it is done once the user is created and logged in. Not sure if there is any way around this.
Here is a snippet of our script:
#!/bin/sh
user=$(ls -la /dev/console | cut -d " " -f 4)
plist="/Users/$user/Library/Preferences/com.apple.dock.plist"
/usr/local/bin/dockutil --remove all --no-restart $plist
sleep 2
# Browsers
/bin/test -e '/Applications/Firefox.app' && /usr/local/bin/dockutil --add '/Applications/Firefox.app' --no-restart $plist
/bin/test -e '/Applications/Safari.app' && /usr/local/bin/dockutil --add '/Applications/Safari.app' --no-restart $plist
# Apple Apps
/bin/test -e '/Applications/Final Cut Pro.app' && /usr/local/bin/dockutil --add '/Applications/Final Cut Pro.app' --no-restart $plist
/bin/test -e '/Applications/DVD Studio Pro.app' && /usr/local/bin/dockutil --add '/Applications/DVD Studio Pro.app' --no-restart $plist
/bin/test -e '/Applications/Compressor.app' && /usr/local/bin/dockutil --add '/Applications/Compressor.app' --no-restart $plist
# Adobe Apps
/bin/test -e '/Applications/Adobe Acrobat DC/Adobe Acrobat.app' && /usr/local/bin/dockutil --add '/Applications/Adobe Acrobat DC/Adobe Acrobat.app' --no-restart $plist
etc...
# Microsoft Applications
/bin/test -e '/Applications/Microsoft Word.app' && /usr/local/bin/dockutil --add '/Applications/Microsoft Word.app' --no-restart $plist
etc...
etc...
etc...
killall cfprefsd
killall Dock
The docks plist file is wiped clean, dockutil adds the dock items to the plist and at the end of the script we kill the dock and have our default dock!
Hope that helps.
