Flat earth with clouds
Travel around the flat earth
The red line is the route of the first ship to travel around the earth. Traveling around the earth is used to prove that the earth is a globe. But as this picture shows, there is no reason why it would be impossible to travel around the earth on a flat disk.
Airplane routes
The green lines in this picture are air company flight routes. As you can see none of them cross Antarctica. Nearly everyone goes via the north.
Sun and moon over the earth
The sun and the moon are spotlights making circles.
Horizon
There are many aspects attributing to the horizon. The most important are perspective and the fact that the air is not fully transparent. You can see that in this picture. The farther the mountains are, the bluer they get, until they merge with the blue sky entirely! We can't see distant mountains, not because they are behind a curvature, but because they fade away in blue mist.