If you look below the two physical drives that you used to have there, you'll notice a brand new drive, the Software RAID device that has one partition below it. That's your future /home partition, sitting happily on a RAID array. If you arrow over to it and hit Enter, you can now configure it just as you would a real partition.
The process is the same for any other partitions you want to toss into RAID. Create identical-sized partitions on all participating physical drives, select to use them as RAID space, enter the multidisk configurator (software RAID), and finally, create an array that uses the real partitions. Then create a filesystem on the newly created array.
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