Again, make sure the target drive is "clean", in other words, not partitioned, and not formatted. It is called "free space", or unpartitioned space. Gparted can do that. The sabayon installer should be able to do that too, but I have had some "issues" with using sabayon installer to delete lvm partitions. Anyway, after you have cleared your target drive of any and all partitions, you can boot the livedvd and start installing. After the first few pages you will have an option to use "custom install or partitioning". Choose that option.
Your target drive should be visable in graphic format, and it should be all "Free space".
Now create a partition, make it "file system type" = swap
Make size = 4000
Ok, now create another partition with:
mount point = /
file system type = ext4
size = 60000
That would be a 60 gb partition. You can increase the size according to your taste, but 60 gb would be close to minimum for a decent test.