We play Mahjong every Saturday, or should I say we are learning.  This model is a rack I designed and printed which can be used to hold the tiles, melds and to build the wall.  The black line is just a color change to allow players to fit the tiles for the wall build without having to count them, allows for a faster build out of the wall.

Tile size: 34.5 x 25.6 x 17.9 = 1-3/8 x 1 x 3/4

You may need to print this in 3 sections and glue them together.  I used the slicer to create the pins.