Keith,
Hosta hybridizer Fred Smith once told me that if you can see dirt, plant another hosta! If I had a 12" area, I'd chose 3 totally different hostas and plant them in there. My choices would be Blue Mouse Ears, Frosted Mouse Ears and Dancing Mouse. Or, Praying Hands(an upright) with a couple colorful small ones under it. You can check Don Rawson's mini list on Hostalibrary.org to get lots of suggestions. Enjoy them for a few years and when they outgrow the area you divide them and plant in another area...or share them with a friend! I have yet to meet a friend that won't take a free hosta!
Have fun with your empty space
