When I make cookie dough, I find it hard to not make a mess when adding the flour to my creamed butter/sugar/egg mixture. If I don’t use parchment paper to help me out, it seems like the flour goes everywhere except into the bowl. Here’s what I do: 1) After sifting the dry ingredients, whisk everything together to help incorporate the mixture (it’s best to do as little mixing as possible once the flour goes into the dough to keep the cookies from becoming tough. More info on that here). 2) Pour the flour out onto a piece of parchment paper. 3) Move the flour to the center by lifting the sides of the parchment. Try to get the flour away from the edges so that it doesn’t spill out when you lift the parchment to the bowl. 4) With the mixer off and the bowl lowered, pour the flour in all at once. For more information about making and storing cookie dough, read this post.