I used a spare one from a water system I had for my feeders, it's intended for holding hoses like misting systems have. You can probably find something similar at a hardware store. I don't know what the name of the part is, sorry.
Some people manage to mount directly under the panel, but I just hang it down the wall like in the picture (I never found an easy and effective way to suspend it, so can't advise on that haha).
Either against the wall or directly under the panel works if you test and adjust the temperatures first. Against the wall like mine will likely be set below the hot spot temperature since it will read ambient temperatures near the wall. I just use a IR Temp Gun to read the hot spot on the floor and adjust the thermostat settings accordingly. (So for me with my household temperatures, I can set the herpstat to 85 and when the probe reads 85, my hot spot below the panel is 88-89 and my cool end is 78-80)
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