Hey. I have mines inside the viv (if outside, the heat won't get through the wood properly) and on the floor. As long as it's on a stat it's all good :)
1.1.0 Corn Snakes, Oscar the Golddust Motley, Emmy the Ultramel Anery 2.0.0 Cats, Yoda and Ed 1.0.0 Leopard Gecko, Masuka 1.0.0 Western Hognose Snake - Hugo
Mat should go inside the viv, on the floor. Stat sensor on top of the mat too as that is the temperature that you want the stat to regulate When your thermometer arrives, it is a good idea to elastic band the probes together so that they are reading the temperature from the same place.