hey not trying to steal this tread but i am in the same situation and i just got my thermostat and just set it up yesterday this is how i did it. I hot glued my probe to the inside of the bottom of my tank in between my terrarium liner(green zilla carpet) and the paper towels that my ball python lives on i have hides on top of the paper towels so she cant get underneath the paper towels or terrarium liner and i also hot glued the probes cord to the side of my tank so she cant get wrapped up in it.
The reason why i didnt put it how everyone is suggesting(under the tank stuck with the heating pad) is cause the temperature that i have my thermostat set at wont be the temperature of the hotspot cause the heat has to go through the glass, carpet, and a layer of papertowels so i would have to use my temp gun to make my hot spot the right temp but my thermostat would read a way higher temp cause the heat loss that the glass and carpet absorb.

please give me your inputs i think that the way i set it up is safe for my ball python but i could be wrong.