Is there any prblem with putting the challa that one is mafrish when baking in your oven? Does it treif up the oven, or the baking tray its placed on?
The challah should not be placed directly on a tray, for it makes it treif (requiring hag’alah). Instead, it should be wrapped in aluminum foil before being placed in the oven or on the tray.
For more details on burning challah, please see http://www.dinonline.org/2010/09/07/burning-challah/, with comment at the bottom.