I was reading the LM2734Z datasheet and in the PCB Layout Considerations section, it says "There should be a continuous ground plane on the bottom layer of a two-layer board except under the switching node island." What is it?
Read a bit more about ground bounce. It's basically the area with your switching supply.
Basically, a switching supply is a noise machine and a solid ground plane can be a bad idea underneath them. I will let you read more from the Analog website because if I could describe it better than them, I'd be working for them.