Let's look at it like this: if space is water as the firmament is supposed to be and the superliquid theorists are accurate, then it's the same principle as going into the sea. The sea will take you to the lowest point you can grasp with your mind, and if you were to go all the way up you would reach the same solution-- liquid water. If you imagine that you have to go down in order to get up, i.e. that in order to reach space you will have to submerge yourself through the water into the earth so as to wind up there then it becomes easier to contemplate what flat earth is based on in reality, since it is a well established ancient concept. We make the assumption that we are traveling in a universal direction such as up, down, forward, left, right, southeast or whatever. If we imagine a straight line then we can continue perpetually in a specified direction but-- that doesn't ever work out perfectly, does it? Aren't we guaranteed to fail at some point and lose our sense of direction? If we rely on equipment, then where is it said that it will always function as intended without distortion or fallacy, absolutely and constantly? In my opinion it will always break down because of mathematics being a struggle to approximate beyond our means of comprehension when a few will do, one or infinite. If perception is riddled with fault lines then we can presume that at some point if we continue as human beings to ascend to the sky by plummeting through the earth (trying to reach space from traveling in the opposing way) then we're guaranteed to acquire a new sense of the path since it will always have to change, and we can only allow for a paradox wherein the reigns of will itself create the flux of any motion.
If we presume that by the time we could reach any center depth of the earth in its flatness that we will arrive in space then we can understand that a half spherical equilibrium rests within the cradle of our ingenuity. We could not use the other half until it is there and we wouldn't know it is before we made it, except in the reality we fantasize about as a presumption for a symmetrical physical consequence to our version of contention with a planetary matrix. Thus to create a spheroid we would need to relate that only half of it would ever be logical for us to require and that in itself completes the wholeness to producing such an object!
A dome is not different than an ozone layer so why bother going into the rest?