Mixing together the dough on a cutting board or other work surface is how the pros do it, rather than in a bowl, which would also work if that makes you more comfortable. Be sure to allow the dough to rest for at least an hour before rolling it out, as this will make that task all the easier to do. While it's resting, you can prepare the filling, and while the pie is baking you can whip up the meringue for the luscious topping.