The Flat Earth is laid out like the United Nations logo. The North Pole is at the center while Antarctica is at the rim. The continents are spread out around the North Pole.
Circumnavigation on an FE is achieved because on a compass East and West are always at right angles to North. Thus traveling Eastwards continuously takes you in a circle around the North Pole. East and West are curved.
North is Hubwards, South is Rimwards, and East is Turnwise, and West is Widdershins
As it happens, even on a Round Earth the "directions" of East and West are also curved. It is a misconception that "East" and "West" are straight directions in either model.
For example; if a man is standing twenty feet from the North Pole on top of a Round Earth and decides to travel Eastwards continuously, his path will take him in a circle around it.
Traveling in a Straight Line
Q. Can't we just circumnavigate the earth by traveling in a straight line without a navigational aid?
A. It is not possible to travel in a perfectly straight line for very long without a navigational aid.
It's not even possible to drive down a long length of highway without turning the steering wheel left or right. Get in a car and see if you can drive down a long stretch of highway without turning the wheel left or right. It's a near impossible thing to do. And when it comes to planes, ships, helicopters, et all., no craft has the ability of traveling in a perfectly straight line without the operator adjusting the craft with regards to visual terrain, compass readings, or what have you.
When one navigates, hands on control is paramount. You wouldn't find a ship captain in New York pointing his vessel in the direction of London, turning on cruise control, and then taking a three week nap in the lower decks. Who knows where he'd end up.
Q. What about other types of navigational instruments?
A. Using a compass, gyrocompass, or looking at North Star as a reference for Eastwards or Westwards travel will take the navigator in a broad circle around the North Pole.