To construct a copy of ∠BAC using point D as a vertex for the new angle, the next step Saadiq should take is:
Saadiq needs to draw an arc on the auxiliary segment using point D.
This step involves using the compass to draw an arc centered at point D that intersects both sides of the original angle ∠BAC. After this, he can determine where to place the new angle's rays based on the intersections of the arc with the sides of ∠BAC.