Paul... pretty sure she got the grills in Walmart and then built the cedar "box" to suit their width. I'll ask her tomorrow when she's home. She's gone for the rest of the night.
It doesn't really show well sitting on that carpet... but in the bottom.. that's a piece of "cement" board, that you would use behind shower tiles. There to take the heat from a burner or similar.
She's not really happy with the end product.. but she never is, even with every screw hole counterbored and plugged etc. I can never get my head wrapped around that kind of detail... lol