What two angles are required when drawing an isometric drawing?

Almost any angle can work. The angles you pick will establish the viewpoint. A viewpoint from a 5 year old kid will look different than a six foot man. Changing the angles are how you change the perspective. You could calculate exactly what angles you want by using a little bit of basic geometry. You will need the distance from the object, size of the target object, and height of the viewpoint. Then you can draw out a diagram and solve for the unknown angles.