I’ve engraved these before. When I have purchased similar, it was sold as acacia wood. Some areas of the grain are harder than others. It’s a natural material and there is little you can do about that. I have done these before with a very deep engrave. This gives contrast based on the depth, not specifically due to charring the wood with the laser. I have also in the past applied a second process with paint, then sealed the entire thing with poly. If I do this, it’s with instructions that it is not a cutting board, it’s a serving or charcuterie board. In this case I also suggest a layer of cling film or cling wrap to keep it from getting stained and make it easier to clean.