Hill starts on an automatic are nothing. As soon as you let off the brake the torque converter will more-or-less hold the car in place until you get over to the accelerator pedal. There used to be (hell maybe still is) a bad-habit of drivers where they wouldnt use brakes at all while stopped on a hill and just let the transmission “hold” the car in place. This is bad because it causes the transmission to heat up from the excess pressure and it’s unsafe.
If the hill is steep enough, gravity can overcome the transmission and you can roll backwards, but just press on the go pedal and you start going forwards. There’s no stalling, just “slipping” internally in the transmission at the torque converter, which is exactly what it’s designed to do.