if there were exactly one point source of radiation it would matter, but there isn't. You have to integrate the cumulative radiation from all the points on the surface. The number of points in a subtended angle goes up as the square of the distance from the bread, and each points' contribution is the inverse square of that distance. This is true uniformly over any subtended arc, so the shape can't matter either. The result only depends on the emissivity of the material.