Help i am baking a 11 x15 cake and everyone suggests to put flower nails in it. how and when do i put them in there?

Prepare your flower nails as you do your pan. I use homemade pan grease and just slather it on the nail with a pastry brush, or you can grease and flour the nails instead. Place the nails flat side down on the bottom of your prepared pan, pour batter in carefully so you don't move the nails and bake.