I found a way to get your farm fields up and ready fast.
First you conquer the level flat that has the level of the NPC you want there.
Collect the valleys, once you have a few (depends on your level), you click on them one at a time, and build a city, spacing the time out between them, you will want time to abandon.
once the first one is built you need to abandon fast (you will loose the 250 workers there). then get ready to abandon the next.
with practice you can build 5 NPCs in 20 minutes not counting the time to conquer the valleys