How many pancakes? 10

J I H B C D A E F G 
1. Flip at: G

J I H B C D A E F G 
2. Flip at: B

J I H G F E A D C B 
3. Flip at: D

J I H G F E A B C D 
4. Flip at: A

J I H G F E D C B A 
5. Flip at: J

A B C D E F G H I J 

The stack is sorted.