This.

My advice is to get your bike between a door frame at your home, lean against one or the other of the jambs, clip in and practise clipping out again 40, 50 or 100 times in the position that feels most natural. Then go outside and ride your bike in an empty car park and practise the routine of unclipping, braking, stopping and putting your foot on the ground.

That routine is what you want to get instilled into your legs and feet so when you have to do it without sufficient warning, you will do it automatically.