All my CP-related blog posts show a step-by-step formulation of the model. Here is an example showing my thought process while modeling the generation of crossword grids using CP (note that this is substantially more complex than the Domino Fit model): https://pedtsr.ca/2023/generating-crossword-grids-using-cons...

Oddly fitting, I wrote this many years ago that you might like: https://andreasscherman.com/posts/an-introduction-to-constra...