I take it you have a notify script triggering policies as part of your Jamf Connect Prestage Enrolment workflow?
The easiest way I've found is to customise the dock on your Mac, then drag and drop the file "~/Library/Preferences/com.apple.dock.plist" into composer and build as a DMG, adding that to a policy with FEU and FUT selected. You can obviously then call the policy from your Jamf Connect notify script.
There's other ways of doing it though, you could install Outset and have that launch a custom Docklib script to set the dock upon first login.
Both methods have worked for me previously, the Docklib method is nice because you don't get the question mark in the dock if an app is specified to be added to the dock but not installed.