This is a tactic that we have used since server 83 back in 2016. I believe RFA were amongst the first if not the first alliance to ever utilise the method.
Firstly you need a keen alliance.
Secondly you must build a farm that has no territory, you can make the alliance buildings but (not the castle) remove it after.
You need space for 500+ territory for union teleport.
You will need 25000-30000 alliance points on the farm alliance per port party changes occur with flag placement lakes and mountains are not included as owned territory.
After setting the farm alliance in your chosen position(next to an enemy) you will Union the farm with your main alliance.
At this point people usually need to restart the application so that the unions appears as active.
As soon as the Union is active and both alliances = more than 500 territory, your alliance is free to use territory teleports to move for 2800 alliance points or 700 gems 1 way. This is opposed to 2000 gems or 7500 points for elite teleports.
The type of attack you use will be dependant upon the timescale of the server. Attack/defence articles and march compositions are the next to be wrote and there will be several