Don’t treat this specific setup as formation, this is caused by specific market behaviour. And a lot depends on some specific details in order to make this formation successful. In general schema looks as follows:
Firstly, we need to see clear trend with impulses and corrections. Then at the extreme point (bottom or top) we see sudden and strong impulse to opposite direction to previous trend. Very often in that extreme point where market makes reversal, we also see volume spikes. Key point is to observe whether market accepts new prices. When the price finishes v-shape reversal, I start looking for reversal.