Even the 802.15.4 2.4GHz Freescale technology is growing on portfolio and each application has its own unique details, the basic RF circuitry can be copied from Freescale reference designs, those has basic layout design considerations need to be take on consideration, the following document on Chapter 7 give some guidelines, concepts, tip and tricks on the RF design, such as PCB stackup, components, antenna and harmonics on a designs.
http://cache.freescale.com/files/rf_if/doc/ref_manual/ZHDCRM.pdf
But if you required more specific information about the new MKW2x devices, the following Application Note will help with some Hardware Design Considerations and package information.
http://cache.freescale.com/files/microcontrollers/doc/app_note/AN4957.pdf
