Is birch ply my best option?

Hi,
I'll be wanting to make light engravings on a flat wooden board about 30x30cm in size with a depth of under 20mm.
The detailing I'm wanting to CNC is text or simple decoration, at about a depth of 0.5 mm deep, and then staining it.
I have basically assumed birch plywood is the way to go, I know cheap plywood can be poor, I've found HPC laser plywood, probably the 6mm deep stuff which seems to be well received without warping etc- it's very important to me that the boards are pretty flat.
Is this the best option for me?
Thanks,
Mark.

Birch ply is good stuff, I think 6mm has 5 laminations of 1.2mm thickness but looks a bit plain, you could glue your own exotic veneers to the top of the plywood. To ensure it keeps flat you should also glue a 'balancing' veneer to the back, this could be just a cheap veneer, you need to maintain an odd number of laminations. If you do fancy the veneer idea then MDF could be another option for the substrate. Very thin birch ply would maybe struggle to remain flat but I think 6mm would be okay.