Thermostat gasket leaking AGAIN!!!!

Jfive, set the neck on a cd case black side, hold it up to eye level, then try to shine a flashlight under it toward you. You could also try a small cake pan bottom. Nothing around the house is that wide and perfectly flat but those are kinda close. Can you take and post pictures? It isn't adding up.
will do. I’ll post when I can. Thanks