Start installation by running OSInstall.mpkg from mounted image. There is no need to create "install partition".

What I've done to get it working:
- Installed SL to separate partition by running OSInstall.mpkg
- Installed latest Chameleon to SL partition + replaced BOOT file with SL-compatible one by netkas
- Replaced mach_kernel on SL partition with my system (AMD-based) compatible one
- Added necessary kexts to Extra/Extensions folder on SL partition
- Added dsdt.aml to SL partition root
- Added smbios.plist to Extra folder on SL partition

Note: I've edited two files to add SL partition UUID to (smbios.plist and PlatformUUID.kext/info.plist)