I volunteered to make a cookie cake for a good friend's son. I've made them before...a billion years ago. My plan was to make my chocolate chip cookie dough and get a disposable pizza pan. Pat out the dough in the pan to an even thickness, maybe 1/2-3/4 inch thick then bake it about 25 degrees lower than normal to prevent the edges from getting too crisp. Does that sound about right? Also, how do I determine serving amounts?
Be sure to leave at least 1/2 inch or more between the dough and the pan if you don't want it to rise on the edges. I also use parchment on the bottom. I use a regular cake pan and cover the sides with baking strips to keep the edges from browning faster if it happens to hit the sides. I'm a little OCD about baking, but this works for me. The lower temp is a good idea.