You made a couple of mistakes.
You do not set faceUV[3] to the material you set it to a vector4 giving the coordinates for the uv values.
When setting the boxOption you must set the boxOption properties to their values not just list the values
Also you must set the blank faces to a zero vector4 value.
eg https://playground.babylonjs.com/#RARJIG#2
Full details and examples on how to do this and how to orientate the angle of the text on the face can be found in the docs Map Materials to Individual Mesh Faces | Babylon.js Documentation