The idea would be to make the main outside surface and trip away the bottom hole, but you’re going to need a few more curves to define the shape.
Use BlendCrvs to fill in the area that will be trimmed off.
Then you can make a NetworkSrf but it won’t fit the hole edge very well without more verticle cross-section curves, probably one more on each side that pass through the hole edge. Probably about here and here:
You’ll probably need to point edit and tweak them to imply the shape you’re after.
Then use NetworkSrf to make the outside surface, trim off the bottom and you’re almost done.