@rotuts, I can put a full half sheet pan on the top of the Anova Oven. It doesn't interfere with the vent on the top of the oven at the back, nor does it interfere with the door to the oven. And the pan does not touch the water reservoir.
IIRC, placing an oven pan with duck fat in it on the top of the oven while on will probably cause the duck fat to melt. But I leave pans on top of the oven all the time.