Applying 6 different textures to a cube at runtime

I can do the UV map and apply it to a cube. And I can apply a different texture that replaces the entire texture, but what I don’t understand is how to make it easy to change one side of the cube to a new texture? I’m guessing I need to use shaders but I don’t understand how to just impact one side of the cube without replacing the entire texture.

What is the best way to do this?

Edit: Looking at using a mesh instead of a model. Does this make sense? Should I go this route?