(...............)
I've routinely stalled our club's Blanik from coordinated turns, and
other gliders, too. Establish a shallow banked turn (10-15 degrees,
say), then simply slow down while maintaining a coordinated turn. At
some point, the inner wing falls and the spin begins.

Coordination is important, but not sufficient to protect you from a spin.


Correct, coordination and speed will do.

If you banked a little more and kept flying coordinated you would at one
point reach the aft limit in the Stick travel and not be able to stall /
spin...