Image is a template I made (thin cardboard) to apply Skin Tac to the appropriate area (avoid sensor insertion spot).
I use it by first cleaning skin with alcohol, let dry, use Magic Marker to make a couple of marks on my skin so that I can tell where to install the sensor after applying Skin Tac, hold the template aligned with marker marks, apply Skin Tac, remove template, give Skin Tac a few moments to dry a bit, and then install sensor using marker marks as a guide so that I don’t accidentally install the sensor thru skin that has Skin Tac on it.