This is the process I use to make many of my free-form copper pieces. When I first started experimenting with this process I ran into SO many problems and couldn't seem to find much information about it. Now that I feel like I know what
QT: Slip Sliding Away: Do your tiles slide on you when working vertical? Here's 3 solutions: use smaller tesserae; make your thinset thicker; or use painter's tape and tape your piece in place until it dries.