I carried a Walther PPK in a homemade IWB holster for many years - sometimes even in uniform. (Even with the Ike jacket.) It must have concealed well - neither the American military nor the German police noticed it. Back then I had not heard of "IWB". I just improvised.
I've carried a Star PD in an Alessi IWB for more years than I dare discuss - long before CHL came to Texas. It must have concealed well, I wasn't arrested. The Alessi won't pass the "shake test" so I can't recommend it for those who "tussle".
My next IWB will have two separate, changeable belt loops (with Chicago screws) to fit belts of various widths.
I tried several "on the belt" configurations and for my rotund shape they didn't work. Even the fine holster by "Roy Baker the Pancake Maker" stuck out too far for me, especially when I twisted to the left or stooped to pick up something.
On the other hand, wearing a winter jacket (ski jacket/field jacket) I have concealed a S&W N-frame .357 with a six inch barrel by using a belt slide and putting the muzzle in my side jeans pocket. This "make do" wasn't neat or confidence-inspiring, but I needed a handgun with me and that was all I had at hand. Believe it or not, I could still sit comfortably and draw that ole Highway Patrolman - even while driving a car.
For a while I carried a Charter Arms Bulldog .44 Special in the elastic portion of my backbrace. Wore shirts I didn't like so if I had to sacrifice the shirt buttons or shirt it wouldn't matter.
Once I carried a shotgun on a cord (over my shoulder, tied to the trigger guard) under a raincoat. But that's outside the "waistband or belt" topic.
I have been compelled by circumstances to improvise so many times, I deeply appreciate TFL. In fifty years, I have never met so many folks who know so much and are willing to discuss it all. You talk - I listen and learn.