Use the soil from the hole to build up the low side. If it is a pretty steep slpoe, you may need a reatining wall to hold up the weight of the soil and water.
this is the only pic of my pond that i have on this computer right now, please excuse the rubber ducks, they were put in for a party i was hosting. The demonic fishing boy has also been removed, it was a gift from my grandma, and she was at the party.