entering a spin on the turn from base to final is not going to be salvageable by anyone.
Yes. So, fly a properly dimensioned circuit, fly the proper speeds, and if it's going outside the lines, go around. If a pilot is doing something other than this, they are not following their training, and making it up as they go along. The designed in safety margins cannot protect you, if you do not stay inside the margins!
I am also partially guilty in practicing a stall and incipient spin recovery without instructor once (with HASEL checks of course, and after a recent practice with an instructor on board, but still a bit dumb thing to do)..
Not dumb at all! As long as you entered this planned practice in an appropriate area, at a safe altitude, and in a suitable airplane type. You planned by reviewing the stall and spin recovery procedures in the flight manual (which are published, as it was a spin approved type), and you chose the right place in space. It is important to remember that an airplane which is spin approved has demonstrated that: It is not possible for the spin to become unrecoverable with any misuse of the controls (Recovery will be delayed, but when you get close to correct control input, it'll recover), and, spin recovery can be accomplished without requiring unusual pilot skill, alertness, nor strength - those are the prevailing requirements for the design approval. Now I agree that if a pilot has never had any instruction about spin recovery (a sad situation), aggressively practicing spin entry is a less good idea. Get some competent training - go looking for it if you have to, it's out there somewhere....
Now, as Megan, and so many others correctly state, any spin awareness a pilot has will be of little use in the circuit, where many spins seem to happen. That's the spin avoidance aspect of things, 'cause recovery will not work. Spin awareness at altitude is more about getting used to unusual attitude recovery, recognizing ground rush, and general pilot skill. Spin approved airplanes would not be so if safe recovery were not easily possible. It is noteworthy that all certified single engine planes, with an exception I'm aware of *, have demonstrated recovery from a one turn spin, even if not spin certified, though spin recovery of a non spin approved type may require extra pilot skill - but with correct technique - will recover.
*The exception I'm aware of: The Cirrus SR-20, by FAA Special Condition 23-ACE-88, which in small part reads [the "system" being CAPs]:
(b) The installation of this system allows relief from another part 23 requirement, spins.
So that can be interpreted to mean that the requirement for the plane to demonstrate recovery from a one turn spin was relieved, rather than required to be complied - because of the presence of the CAPs. So, I cannot state that the SR-20 will recover a spin, if flown with skill, as all other certified singles could. But Cirrus knows, as do we, that a well executed spin recovery will be useless, as will CAPs deployment, at low circuit altitudes.
the NASA designed cuffed wing is actually quite difficult to stall.
Perhaps, though it seems that spin recovery compliance was compromised.