The problem you are facing is that they are under the impression that your senses can be trusted above all else. This is patently false as proven by flight simulators.
Anyhow, the other problem you face is that you will constantly be attacking a strawman, but that isn't entirely your fault. You see, Flat Earthers don't have a single model they can utilize that will make all objective observations make sense. Let me give you an example:
Flat Earthers claim that the Sun rotates above the Earth a few thousand miles and the Moon is opposite the Sun's position and this accounts for the day/night cycle. Then, they also claim, that the Sun moves between tropics to account for the seasons/equinoxes. The problem with these two hypotheses is that you can't use ONE model for both of these observations. Matter of fact, if you use one, then you contradict and disprove the other. Let me explain: If the Sun and Moon were just a few thousand miles above the Earth, then they'd have to account for the objective fact that HALF the Earth is in daylight while the other is in darkness......
If the Sun were to be the source of the light during the day, then NO amount of physics can account for exactly bisecting a circle periodically with a flashlight (the Sun)......UNLESS that flashlight has a shape-shifting lampshade which forces the projected light to periodically bisect the circle. Also, since the Tropics are not the same circumference, that means the Sun has to travel at different speeds during the seasons and give differing amounts of daylight. This graphic will explain what I mean.....
The Tropic of Cancer is much smaller in circumference due to math and logic than the Tropic of Capricorn which means the Sun travels faster during the Summer than in the Winter when it has to travel a much larger circumference. We do not see this, though. We see the Sun moving through the sky at the same speed regardless of the season @ 15 degrees each hour/day.
As I stated before, each model can explain an observation, but there isn't ONE model that can explain BOTH unlike the globe model.
Flat Earthers don't have a model that can explain all the phenomenon we experience/predict, therefore, when you argue against them, ask them to provide a model that can, otherwise, they will just continue to claim that YOU are arguing against a strawman and don't understand science when it is actually THEY who argue from ignorance/incredulity as they cannot think in 3D and do not understand the globe model.
