Hi eric, so the different way of creating a solid block and then carving it up would go like this - start by drawing a profile curve in the side view to get something like this:



Now extrude that to get your starting solid block:



Now you can go to the Front view and draw in some cutting curve profiles, like this:




Select the solid block and run Construct > Boolean > Difference - this will slice the block by those front profile curves and leave it in pieces like this:



Select the outer pieces and delete them to get the result:



This method tends to be an easier way to work on things, particularly when you want some kind of curvy surface portion - instead of trying to build a curvy surface to some irregular outline hole you instead want to have the curvy surface be some larger extended sheet that gets trimmed where it intersects the other shape. Using cutting and intersections as a primary modeling tool in this way is one of the biggest differences between NURBS modeling versus polygon modeling.


You can also rotate the cutting curves in the top view if you want them to cut at an angle:





If you're using a line as the cutting curve and want to make it cut at an angle, you'll need to extrude it out into a cutting surface and use the "Set dir" option in extrude to control which direction it will go in, because a line does not have a single inherent perpendicular direction like a planar curve does.

But if you want to make cuts that go straight out from one of the side views, you can draw cutting curves in those views (including lines flat in the view) to do those cuts.

- Michael