He uses veneered HDF (High Density Fiberboard) for his layered projects, but he says you can use plywood or hardboards. I think that is because what he uses is hard to find here. I have found medium density fiberboard and my local Home Depot, but it is not veneered. I sent him a message a couple of months ago and he was quick to respond. I think he probably gets a lot of requests because he sends a nice explanation of his entire process. I you click on his picture you will find in the top a little envelope. Click on that and send him a message. That envelope is his email address. By doing this only the two of you are involved. If you have questions don't hesitate to ask.
Jerry Walters