Believe it or not, Brazilian Jiu-Jitsu isn’t that complicated at all. Sure, there’s like a million techniques out there and, yeah, there’s like a billion (ok, maybe a bit less) variations to them… But, when you decide to focus on the high percentage stuff and those techniques which open the doors for a lot of different setups – BJJ gets super easy rather fast.
For example, take a look at this arm trap from Open Guard, as demonstrated by Keenan Cornelius. You’ll be surprised at how easy it is to use for a backtake.

WEIRD ARM TRAP THAT LEADS TO BACKTAKES

If you’ve been training for a while, you probably know how to hit an Armdrag (reasonably well, nevertheless). You’ll do it in this scenario as well, for you’ll take the opponent’s arm and drag it… Not across your body, however; but in-between your leg line (your legs).
Once you get the opponent’s arm there, you’ll trap it in-between your legs by clamping them together. From there, drive your arm underneath the trapped arm and establish a sort of a Darce-like grip on it – trapping it in place.

As soon as you’ve done that, the road is open for the backtake. Watch how Keenan Cornelius does it on the videohttps://www.youtube.com/watch?v=uaFcJwGKcZ8 below and take a look at how he goes about the arm trap: