Currently we don't have reference design for WLCSP package.
Both PSOIC4 BLE and PROC BLE WLCSP packages are pin-pin compatible .
You can refer the app notes
Though these are not specific to PSOC4 BLE/PROC BLE you can use them as a reference.
Once you are done with layout ,We recommend to create tech support case https://secure.cypress.com/myaccount/?id=25&source=contactus to get it reviewed.