While I'm schlepping in a rental (without either the permanence or money for a good stone or steel), I've found that the metal trays that came with my oven in addition to the standard wire racks are a lot better than nothing for crisp bottom crusts. I shape my bread on parchment or its floured towel and preheat the metal tray along with the oven, then just slide the parchment onto the tray and listen to the bread sizzle a bit as the bottom meets hot metal. By the time the loaf is done, the bottom crust is dark brown and just as good as the top. I imagine that pre-heating an old, hefty metal sheet pan might provide a similar effect for other folk who have to work without the better options.

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