I made some like that to start, but then I abandoned the idea since I'm not using these as trays with lids. I still have a bunch of magnets laying around to use if I wanted to add the feature back in though. Those little suckers are powerful!
I tried making my own wooden racks but it's not even close to Chanman's quality and craftmanship. I would say that this type project is not for a weekend warrior like most of us. . It's hard to make the grooves straight and evenly spaced.