The three day formation from June 16 through June 18 is a pretty bull flag. SPY bounced off a test of the 18 day moving average on June 16 and successfully turned around a probe yesterday. The bottom on June 18 occurred early in the day, and it was easy to get in.
The table above shows average natural log gains. That is different than the aggregation I usually do.
It was reasonable to buy at the close. Buying at the open is not favorable, but not bad either. The current play is to buy the low.