Have you ever written a Sudoku solver. It works like that.

You start with an array where every tile is possible in every location. Then you pick a random cell and assign a tile to it. That tile implies some choices are impossible, so you set those possibilities to false. That further implies some other possibilities are false and so on. You propogate that as far as it goes, and when you are done, pick another random cell and assign a random possible tile to it.

Because you are propogating information as much as possible before making the next choice, the algorithm very rarely needs to backtrack. You can run WFC without any backtracking at all and it'll still find a solution most of the time.

Some animated examples I put together might illustrate things more: https://boristhebrave.github.io/DeBroglie/articles/gallery.h...