The vast majority of the work here is Slabs, with a Cubes and Cylinders. Sometimes Lines and Lathes. There is very little sculpting with brushes - just a bit here and there to add a natural look. When I needed to make more complex shapes I tended to use Curvy Maps (displacement) and Voxel Intersection (Booleans). When I get really stuck I use a Loft with thickness - Helpful for shapes that bend in more than one direction at once.
And a few of my favorites zoomed in:
