Help regarding IIS 10 configuration for NO default page

MY IIS 10 SETUP:
- static files only ... minimal installation
- directory listing is NOT installed, thus not enabled
- redirection is NOT installed, thus not enabled
- the only default directory page is "index.html".

Currently:

given www.mydomain/dir1/ (with no files in it) returns an empty page with a 301 status.

I would like IIS to return error 404 when no default page is found in the directory.

QUESTIONS:

1) Is there a setting in IIS to manage this behavior, and what is its name or reference?

if answer to above is NONE:
2) How can I make IIS return an error 404 upon a directory hit with no default document?

if answer to above is CANNOT:
3) How can I redirect this particular empty page (301 status) to a default page of my choosing.

Thanks