The key is to avoid training too many of your villagers in construction (and doing it too early) with the limited opportunities that you have. I usually wait until I have almost enough research points for level 3 of harvesting to start on the beach. At that point, you should be able to use the construction of any remaining huts and the other construction projects to train one or two builders and be just fine. If you want the master builders for what I think you want them for, you can accomplish that feat much earlier in the game than the puzzle screen would suggest!