Bought the trays from amazon.ca. S&B LEE 358x200F with Smoke's excellent Carolina Blue powder. Baked in the tray. DISASTER! And, didn't do the new tray much good either. As has been said: there's a lot of ART mixed up in this science. I'm not saying the 'tray method' doesn't work........I'm just saying it doesn't work for ME. I'm back, happily, using my hardware cloth grids and made-up holders shown in another post about Standing Tall Boolits.
YMMV.