Question: Sometimes we don’t have a 4th player. Is there a way to play with 3 people?

Answer: Yes, absolutely, in three-handed mah jongg, the walls are built just as in four-handed mah jongg. Tiles are dealt out to the three players but no tiles are given to the to the empty seat. The Charleston is omitted from this version of the game.

Source: Mah Jongg Made Easy 2020 page 26