Having the flat Earth as a solid slab of rock has it's own problems. It doesn't explain volcanoes, it doesn't explain earthquakes, it doesn't explain geothermal energy and without surface tension what is there to hold together such a huge mass of fractured rock?
Having it as a molten mass with a thin solid crust also has it's own issue. The raindrop analogy works wonderfully here. In both cases you have mass of fluid with something applying a force to one side (in the case of a raindrop it's air resistance, in the case of the flat Earth it's the universal accelerator). Such a situation causes a section of the surface of the liquid to flatten, which seems to fit wonderfully with the FE model. This is until you realise that the flattened surface faces into the direction that the force is being applied from, which would mean that underside of the FE would be flat, with us living on the curved surface.