First, I created a 4in x 4in square as a template (to represent the coaster). Next, I created the design in its own layer and centered it within the template. 

Once the design was completed, I secured a piece of cardboard with magnet pins to the honeycomb to secure it in place so it wouldn't move.

If you need pins, these are useful ( xTool Honeycomb Material Pin )

Once the cardboard is secured to the honeycomb, go ahead and cut out the template from the cardboard, and carefully removed the cut piece making sure not to move the rest of the template. Choose the design layer, make sure "output" & "Show" are enabled for that design, all other layers should be disabled. I like to click the preview button to make sure I am only engraving the chosen layer.

Next, when you are pleased with the set up go ahead and insert a coaster inside the cardboard. Then, click frame to make sure the design is in the desired position on the coaster. Hit start and begin. After it is complete, remove the coaster and insert another.

Once the engraving is complete you have a finished coaster. I put a single light coat of clear coat spray paint over the coaster. The coaster to me looks dull but with the clear coat it has a wet darker look to the slate.