What are the other ways to delete part of the mesh?

[miles115]

For example, I want to delete part of the extra meshes like in the picture below but the only ways I know are pretty limited and more time-consuming:

1. Add vertices using subdiv and select all the extra part and delete vertices
2. Add loop cut and delete the faces (which is time consuming as loop cut only add to 1 side so I have to add 4 times
3. Duplicate the shape and line up to the extra part I want to delete and then go to boolean add-n → slice (this is harder to do in this example because the object is skewed/ tilted making it difficult to align to x-axis/ y-axis)

[joseph]

Add a cube. Move it. Boolean. Done. (Not clean, but much faster than any of these methods)

[Okidoki]

Do not delete at all.

Select the face in the middle of the circled area, add a new transform orientation ( plus sign), select more, move along this face normal (as new oriention) to your liking.

[BG_Division]

And you can do the same also just using cursor snapping and using his orientation