If we go back to the original question, flat earth believers have no scientifically derived answer to this question as there is no flat earth answer. Plate tectonics as is studied observed and recorded only works on a globe earth.
If we stay with reality for a moment, GPS, the Russian GLONASS, China’s BeiDou and the European Union’s Galileo have revolutionised the way the ever moving continents are tracked with their positions being constantly monitored. Continents like Australia for example are moving quite rapidly averaging 7cm per annum.
The data produced by these different satellite based systems, relative position of landmasses, only holds true for a globe earth, there is no way this relative positional data can be interpreted to show the earth is flat let alone be flat and infinite!
https://wonderfulengineering.com/how-gps-keeps-up-with-the-continent-thats-in-constant-motion/The fact that land masses are constantly moving is beyond doubt, if the earth were flat or flat and infinite all the continental crust would have moved either off the edge leaving no land, or moved off into infinity to be replaced by crust from the infinite reaches, neither of which is the case.
The problem is for flat earthers, regardless the scientific discipline that is chosen, physics, astronomy or in this case geology all the facts each has to offer prove the earth is neither flat nor infinite.