Yeah the tray just goes on the stone,it doesn't damage the stone, it was never a way to keep the stone clean I just found it easier to use trays in the end, the pizzas are obviously an exact circle and the use all of the stone surface rather than having to try and make one to that size, it also makes moving the pizza around a damn sight easier both I preparation and when the pizza has cooked.
Check amazon reviews out, quite positive and a few good tips.
Do you put the pizza tray in the pizza oven on top of the pizza stone to cook the pizza? Do your pizza trays not damage the pizza stone? Sounds like a good way of keeping the stone clean. :)
I got the Ferrari g3 a couple of years back, there extensive threads on the g3's on here with loads of good advise. Took me a good 10 runs at making my own before I was happy with them,there is alot of trial and error and learning. But get that out of the way and it's so easy to do. Makro do Wright's pizza flour for £12 16kg bag and 2kg bags of mozzarella cheese for £7 I also found 10mm deep 12 inch pizza trays that fit the oven perfectly I find that it's easier and faster making them this way rather than fighting with a pizza shovel.