I like using the Clip Cube; It is like a 3D viewport crop that is…
Vectorworks Tip 333 – Changing the Angle of a Clip Cube
When you start a clip cube it is always orthogonal, but this often does not line up with the model. Rotating the plan does not help, but there is an easy solution. If you select the clip cube with the selection tool, you will see four blue dots at the bottom center of the clip cube. Use one of these to rotate the clip cube to match the angle of your project.