If anyone is thinking of having a go at doing some stone this is how I do mine.

I made a wooden tray up the size of the work area of my cnc and I made the sides 50mm high then sealed the tray with an epoxy resin in all corners and screw the tray to the bed
Then I put the stone/marble/slate/ect in the tray and fill it with water being sure to fix the sides of the stone with buffers to stop any movement and away to go......Keep your tooling covered with water all the time though as they last longer and after every job in stone I changed the water as it gets to murky to see how it is going.
My Next CNC will have a water recycling setup.
Hope this helps
Pete