As a left handed shooter, this is exactly how I do it!I'm going on 60 years of being a lefty in a right handed world. It does have issues. But Glock isn't one of them.
The slide lock is used only for inspection. I take my trigger finger hold the lock up, and jack the slide.
If the slide locks back while shooting, insert mag sling shot the slide, the way Glock designed it.
To drop the mag, the left index finger works well.
The only issue I've had being a lefty is that the mag release is open to bumps while holstered.