Why do you want to build the Galileo's image using split layers? I mean, I'm asking you if there is a specific reason why you don't want to build the image normally, because if there's not, then I would suggest you to build the image by using Quark's BSP.
If that's the case, I would suggest you to read:
The first one is for the Quark's BSP 1.0.1, which is the latest version that was specifically for Galileo. The second one is for Quark's BSP 1.2.1, which is the latest version. 1.2.1 is Galileo compatible but not Galileo specific and has fixed some issues present in version 1.0.1 as well as added some features.
Thanks for the quick response.
I did try both BSP sources and the building guides. Unfortunately, the builds failed. For instance, when building Quark's BSP 1.2.1 in a Ubuntu 15.10 machine, the error was:
ERROR: Layer 'networking-layer' depends on layer 'meta-python', but this layer is not enabled in your configuration
As you can see in Yocto Project Reference Manual, Ubuntu 15.X is not officially supported by the Yocto project yet, so this problem might be related to that. However a user found a workaround for building Edison's BSP on Ubuntu 15, you might be interested in checking it:
What's difference between BSP1.2.0 and 1.2.1?
What's add new function and any update in BSP1.2.1?
You can check what's been updated in the release notes of Quark's BSP 1.2.1: