The diagram here actually does a pretty good job of depicting how the curl flat concept can absolutely flummox defenses. Your first reads will be the two receivers running the curl routes. Keep an eye on the defenders here -- if they're too close to your receiver, they'll jump the route.
For all of the advancements made in Madden 19, the franchise still hasn't figured out how to make receivers break toward the ball on curl routes, so be careful. Much like with the stick concept, an interception here can be absolutely crushing, so if there's anyone even close to your intended receiver, move on.
Luckily, if they're covered, your other two receivers will likely be wide open for a modest gain of 3 or 4 yards. The difficulty in running this play is that these are necessarily quick reads. The play takes very little time to develop; you'll have to gauge whether the receiver on the curling route is open as soon as they turn around. At that point, you'll have to glance at your check-down on the flat and make a decision.
The good news is that if you've practiced the stick concept, the reads are very similar here. If you can run that play, you can absolutely run this one.
Source: Annoyed Football Nerd