That's going to be a nice sized pond. You can build the low end up so the pond is more ground level or you could do something fun on the high end using rocks and/or vegetation.
If you slope that high end so it gradually goes down, it would not be noticed and could be a great place to put plants that like a little more water. Or leave it as a 'cliff' and put some rocks in there for affect.
If you want your pond to have a level edge all the way around, build up that low end. You need only a fracton of an inch for the water to flow out the low end (and, depending upon how much digging you want to do) a deeper pond.
