Either straighten and continue left, or straighten then ride a stride or 2 straight and then leg yield right depending on the situation.
It can be used in reverse as well. Start on the wall (for this example we’re going to the left, (counter clockwise) in counter canter (right lead in this case), leg yield to the quarter line, establish a right bend and half pass back to the wall. Voila, you’ve just used that magnetic quality of the wall to help the horse understand half pass.
How about thinking of that “canter LY” as just “standing the horse up in balance”? Regarding HP, sometimes a horse starts to fall over his inside shoulder. “Pushing” him out in a LY gets that shoulder stood up and him balanced back over the outside hind. Eventually it takes just a strong inside leg to outside rein to do that (otherwise known as a half halt😉) maybe one stride of “slightly less angled HP”…
Short story. I have a PRE who knows all the tricks but really has holes in his foundation. When I first asked him for the LY at canter (my trainer calls it a plié), he almost fell down. Really. So I started easy with just a few steps of drifting out over the outside shoulder. Really has improved his overall balance.
You can also imagine that plié down the long side as a strong “sort-of shoulder in” (without much bend except that which the canter itself provides) down the wall.
Understand that was probably from shock of being asked to shift his balance in a completely new way and that once lorilu asked for less (a drift) he was fine. If a horse has giant holes in their training or gets asked for anything at any stage that is completely new and perhaps asked for a little too emphatically (or the horse responds too enthusiastically) they can lose their balance.
It’s like horses that compete in Tevis. Do they train on Cougar Rock on the regular? No. Do they build up to that kind of rock climbing in a methodical way, asking easier climbing questions that gradually build in difficulty? Yes. Just as with that, and with, say, full pass, we start very gradually, barely asking anything and then build as the horse understands. We don’t suddenly tell our horses that today we are doing full pass, we work on making the half pass steeper, or if we’re not there yet, we work on getting a very shallow half pass - maybe 5m sideways over 20 or 30m of length.
How about the shallow loop found in lower level tests? Or, Just start on the quarter line and just ask him to move off your inside leg one stride.
Start small.
Or just doing the “enlarge the circle” exercise-20 meter circle, at the open side of the circle just “enlarge it” ….
That canter leg yield is just a stepping stone for your flying change- feel the balance and use it to help create the correct alignment - then ask for a change! Some horses benefit more from that than walk canter walk on tight circles for the change.