Converting a self-intersecting surface into a solid

[ahmed3ZMZE]

Given the following surface, built using a closed path and a sweep profile,

there will be a self-intersecting surface:

A simple patching of the upper side works, but fails on the lower edge since it is self-intersecting. My goal is to build a solid body; what can I do?

For context, this is a contrived example to demonstrate my goal of building a volcano-like tapering of the sides of random sketch shapes. It is worth mentioning that I have tried to use a loft operation with an intermediate offset of the sketch shape, but got some weird behaviour. It would seem like this would be rather straight forward to implement, but I am new to CAD, in general, and F360, in particular.

FWIW, here's the link to the design: https://a360.co/45o947p

[TrippyLighting]

That cannot be done without creating interior surfaces, which will likely lead to continued modeling problems.

The boundary fill tool can create a solid, but if you use the section view tool in the inspect menu, you'll find that you have interior geometry, which should not be the case.

A loft to a 2nd profile is definitely the right tool.

[ahmed3ZMZE]

Fair enough @TrippyLighting , but wouldn't then make sense for this loft functionality to work consistently across the profile? Why is there a "crease" in the resulting solid?

Am I missing something or is this a bug?

[ahmed3ZMZE]

Seems that the "Direction" option for the profile option in the loft dialog helps and even precludes the need for an intermediate (middle) profile in this case. However, with a slightly more elaborate base profile (the one that defines the "volcano mouth" shape), self-intersection happens for some reason. I will follow up on this as soon as I get your feedback. I appreciate it in advance!

P.S. Rhino 7 has a much more predictable loft behaviour and I have as much experience in it as in F360.