Reading this link, it describes how to make a RAID array out of USB sticks, however it describes the process using Gentoo now I don't know about gentoo and have never used it, but I'm supposing this is possible in Ubuntu if so how?.
Create a mirrored partition:
4 disk RAID 5:
The guide that you linked will be the same with ubuntu. The raid utility "mdadm" is fairly common and well documented.
You will need to