Step 4: Draw the gravestones as vector images
Use your favourite vector image design software (I used Adobe Illustrator) to draw out your gravestones. As you do, think about how they will be etched by the laser cutter.
The laser cutter works by burning away a thin layer of material in a single plane on the surface of a sheet of acrylic. By burning away successive layers, you can gradually carve away a 3D object. This is quite a limited approach to 3D fabrication, as it cannot produce complex objects with overhanging features. What's more, it's very slow; each pass of the laser may take several minutes but only remove a tiny fraction of an inch of material depth.
Shade your 2D vector images according to the different depths at which you want to etch them. In my images, I used darker shades of grey to indicate where I wanted more material to be etched away (except for the cilantro stone, where I deviated from this scheme for the sake of contrast).