There is not a spot in this house that is level. The tiles do not lay flat, and this is the main cause of them popping up. I bought 3 50 pound bags of self-leveling floor cement. It was our hope that we could pour the mixture and end up with a floor that could be tiled.
The floor had a high spot close to the middle, and it ran higher on the left side. We poured two bags of the cement and got the floor to about the highest point that we could. We did not want to get to the point of stepping down into the bedrooms.

The floor is a lot closer to level, but not quite there. We will attempt to lay the tile soon.