I am concerned that the queen excluder is slick and the flow hive box will slide off, anyone else have this problem?
Not at all. I did a hive inspection on Sunday. The Queen excluder was very much stuck to both brood box and honey super. They had put propolis everywhere, even from the Queen excluder to the brood frames below.
My bees are doing pretty well at sealing up cracks and hive bodies with propolis. If you’re worried, you can always place a weight over the lid on the super or use a rachet strap to help anchor the hives to the ground.