"the great flood for which there’s much evidence could not happen on a globe but could happen with a firmament."

If the world is flat, water would flow off. If your reasoning for the flat Earth is that "the great flood could not happen on a globe", then you are advocating for a force to be holding it in place.

I find it amusing that no flat Earthers ever want to put their money where their mouths are and fly to the edge of the planet to prove themselves.