I have also used the black rubber bowls, they can be inset into an old tire. Insulation can be added to the inside of the tire also, if you set it in a sunny area, the black color absorbs the heat from the sun and this will slow the freezing process down. I also did see where if you add a ping pong ball or other floating ball, the movement from the wind, or chickens pecking at it keeps ice from forming if it is not extremely cold. Also, if you do have to break the ice out, the rubber bowl will not break.
I actually use a method posted by Serious Eats where you fully incorporate the fat into 2/3 of the flour, and then cut the rest of the flour into that. Then I use half water/half vodka for the liquid and fold it in half a couple times as I'm forming it (I use parchment paper or cling wrap). Makes dough that's easy to handle and super flaky.
