Beamer claims to have a \appendix function, but it didn't seem to have much effect. My slides present the slide number and total number of slides in the bottom-right, and I don't want the appendix adding to that total.
I found a solution with the appendixnumberbeamer package. With this attached, the \appendix function will reset the page numbering, results in appendices that don't effect the number of slides.
I'm not going to make a sample, you can figure it out