Dichro on bottom
Yes, the dichro with a black backing can be the bottom layer. Even a clear backing can be the bottom layer. Obviously, you’d want to cap with clear
What I answered indirectly in regards to the black being the bottom layer, is that you don’t want to fuse a single layer of black dichro on its own. You’ll want to cap it — otherwise, the dog-boning occurs, if you take to full fusing temps.
Your best bet in cutting thicker pieces is a tile saw with a diamond blade made for glass, if you have access to a tile saw (and have the approx $75 for the blade).
10 minutes at 1450 should be hot/long enough in most instances, but realize that the firing schedules provided in books are a starting point. A kiln could heat hotter or colder than what the thermocouple or pyranometer reads. The second best thing for a kiln, besides the controller, is a view window (IMO). It’s nice to be able to peek in and see what is going on, without opening the kiln door.
Jester’s Baubles Fused Glass Designs