The general cue to do this move is when you have an omoplata set up, but your partner might bury their arm (typically, inside their own thigh). While this means it's going to be challenging to finish the shoulder lock, this opens up another excellent opportunity.

Start by underhooking their arm, then planting your foot on the mat. This should allow you to drop your inside knee to the floor, completely changing your angle of attack. Now reach with your free right hand to grip your partner's foot or pants, and then bring them to your left (and continue to drive them to your right as you flip your body over to follow them). You should finish in a very tight armbar position.