I practiced with the bike in a trainer.
Also, while balancing in a doorway is supposed to work.
In a grass field if your tires are wide enough to allow it.
Also, in a parking lot where you can practice while at a higher speed is probably good. Since with speed comes stability on a bike. Just go in a straight line and clip in and out...
Clipless falls happen to everybody.
Were there witnesses? There usually are.