Negative space drawings are made by only looking at what is NOT there. There are no internal details in the obkects, because that is not what is being drawn!
This is aided by the use of a viewfinder, where the space between the object and the frame can be clearly seen.
Sometimes it is asier to shade the negative space between the object and the frame.
See the examples below of two stools, a chair and a handtruck from: https://scienceleadership.org/blog/negative_space_drawings_and_cut-outs