So last week I found a seed and typed it in and just didn't bother playing it until today with some friends. When we were exploring the map we found loads of clay not just one tiny area but 10x10 areas to the 20x20's we had 2 chest full of clay all stacked up to 64. Don't get why it's so hard to find! We found it in 5 minutes!
The latest update fixed the little to no clay issue. In a few days the next update should come as well. You can find out more info about the next update and future ones here.