well-I've never actually tried sabayon, but with most distro's-you extract the .iso file-right-click on iso, choose extract here.
Go into the folder, copy the contents of the folder to your USB(select all, copy, paste into usb)
then if there is a isolinux folder, change the name to syslinux, and change the name of the isolinux.cfg file to syslinux.cfg. Now copy the syslinux.cfg file and copy it to the top directory.so you'll have 2 syslinux.cfg files-one in the usb/boot/syslinux folder and 1 in the /usb top directory.
Now, you usually have to edit the syslinux.cfg file, and change where it says "kernel linux24" to "kernel /linux24"-and the same with the append part-like so..
kernel linux24 kernel /linux24
append initrd=initrd.gz append initrd=/initrd.gz
Open a terminal, become root-sudo su,etc, then type "syslinux -s /dev/sdxx"-where xx is your usb drive(sdf1,sdb1,etc)-DON'T do it without being sure-'cause you could install it to your HD by accident and then you will have problems!You'll now see a executable called "idlinux.sys"-that's syslinux.
After that, reboot and see if it works!
If it doesn't work or there isn't a isolinux/syslinux folder, you may have to do a little work.Oh-and that's Slitaz-cooking.iso(30MB) in my USB(4GB Kingston)
If you have problems, add to this post and I'll try and help-cool?
See screenshots too and if your trying to put the Sabayon DVD on your USB see this---