> how to adhere the mat with the whole in it to the backing mat....I know you all know.
Unsure of what you mean by adhering the whole thing to the back matt.
You can't use the drymount press for that. Get double sided framer's tape (3M red outer package, comes in various widths )and use in small quantities on the back of upper matt.
Remember that once you press the 2 matts together, there is no re-positioning. this process will last forever. Never had one come apart, even in our humid climate. Is this what you mean?
Hope this helps,