Crowinghorse, Mike is right. Sharpen the flat edge as you would any knife and then use a ceramic steel or rod to lightly stroke the convex side to JUST take off the burr. The convex design is very strong, you only need to sharpen the convex edge if there is severe deformation. To sharpen the convex edge, just load some strop on a piece of leather and away you go. If you need to remove more material use sandpaper backed on a piece of styrofoam (that allows the paper to follow the convex curve). You can always grind the convex side flat, but you'd really be losing a lot. The convex edge is incredibly strong and worth any "perceived" hassle. Hope that helps.
------------------
"Better to reign in Hell, than serve in Heav'n"
John Milton
There are only two types of people; those who understand this, and those who think they do.