How do you code Random Encounters based on Tiles

Unity Engine
1

I am trying to make a traditional RPG game, like FF but I can’t find any way to code Random Encounters based on a grid from the top down perspective.

2
  1. set a flag on all tiles which have possibility of encounters
  2. when user steps on a tile that has a possibility of encounters, calculate if they are due for an encounter
    2a) how long since the last encounter finished?
    2b) how far have they walked since the last encounter?
    2c) do they have any buffs/charms/artifacts that encourage or disable encounters?
  3. if they are due for an encounter, figure out the enemy type(s) and kick off your battle scene
3

thnx