It's dry mounted, not dry matted. Two different words there. No such thing as dry matted.
1) Cut the mat to the specified size you need for the image.
2) Cut the backing board to the size of the mat.
3) Put the matting on top of the backing board, and trace the inside hole of the matting to the backing board.
4) Set the image over the trace lines as close as possible after applying the adhesive inside the trace lines which are on the backing board.
Step 1 - ok
After that, you are creating more work for yourself than necessary. If you want to spray mount it down you would want to leave the backer board larger than the mat size. Spray the board and place the photo in the middle of the sprayed area. Once you have pressed the photo into place, you then place the mat over the photo and once it is attached , you just cut away the extra backer board to the edge of the mat and you are done.
They also make a board with adhesive already on it. You just peel the release paper off and there it is. Better than breathing the spray!
You never want to trace the opening of the mat as you can get marks on the bevel of the mat and ruin it.
$20 is only alot in respect to how little you can afford. That is a fair price to have a professional do it for you. Alot of beginning artists can not afford to have their work done professionally. Doesn't mean we are ripping you off, just that you can't afford us yet.
There will come a point in your career when your time is better spent shooting than framing.
Like the photographer I have in here with 14 pieces for a gallery. His bill is over $3500 when I'm done but his photos sell for $1500 to $2000 each.
My frame, mat, backing, and glass for an 18 x 23 inlcuding shipping in bulk is about 23 Dollars. I sell the 18 x 24s for 95.00 US. So you can see like you say that 20.00 to have a professional dry mount the image is about 30% of my profit. It's very reasonalbe indeed. It's really cheap if you can sell your images for 200.00 for each 18 x 24.
I did notice that the single hinge works better than two seperate hinges, in my climate--which is very wet.
The backing board with peel off adhesive sounds very interesting. That would be easy.