I can't believe it's just me, but with _any_ watchmaker face, even one I created from scratch with no hotspots or anything, long-press on the face to switch faces doesn't work most of the time. Occasionally it does, but I have to try 5 times or so. Also "OK Google" seems to be much less reliable than with "native" watch faces. I'm running the latest Android Wear (5.0.2) on a Sony Smartwatch 3, SWR50. My phone is a Nexus 5 running 5.1, stock/rooted.
I've rebooted the watch and phone a bunch of times, tried lots of things, but at this point Watchmaker is basically unusable for me -- which is too bad because the faces are incredibly beautiful and useful!