How are the grooves made? 🤔 Like, is the wood a solid piece or does it start out as a sort of pulpy slurry?

I want to say if it was cast into a slurry entirely it wouldn’t have the dark spots in the grooves. I think it’s more likely it was cast as a blank record shape first, and then used a laser based on a 3d model of the record. Just a guess though.