These types of submissions are not high percentage, nor should you base an entire game around them.
Open your elbows up, put your head on the ground above theirs and sprawl your hips...
It works against the straight Ashi Garami position when people are not mindful of their top leg (the leg that is behind your butt)...
Wristlocks have gotten themselves a reputation as being the sneakiest BJJ submissions available and this one is no exception.