I had finished my first game fairly quickly so i was done all the puzzles and there was nothing left to build, but i still got masters in building on maintaining the huts and hospital etc, just a little hint, it goes faster when your not sitting there watching, if you pause then take the villagers and place them where their supposed to be (works for all feilds of work) and then unpause and then exit the game, dont minimize, sont leave it open ,, acually exit the game, and come back to it an hour or so later (depends on the spead you have it running on) they will have gained some skill. but you acually have to place them where they need to be, if you leave them *enjoying the pond* thats what they will do while your away, its not somthing i can say its a trick or any kind of cheat, but its somthing that i have found works for me. and I got about 20 master builders doing that after i had finished all the puzzles and all my collections, and all techs.

Yes, after having built all buildings and completed all 16 puzzles I have turned a villager with no building skill into a Master Builder, and in a reasonable enough time for them to become an Elder as well.