How do you slice cookie dough?

If you're talking about dividing the batter into pans then it easiest the pour the batter right from the bowl into the pans. Make sure the the batter is at the same level in each pan so that the cakes rise to the same level. And if one is slightly bigger than the other than you can always cut scraps off of it.

Then again if you're dividing batter into muffin tins to make cupcakes, it's better to use 2 soup spoons (one to scoop and one to be help under the first to catch any drops that may fall) or an ice cream scoop. Hope this helped