Folding this net, we will have this following pair of squares that are facing each other
the square with number 5 will face the square with number 10 = 5×10 = 50
the square with number 7 will face the square with number 6 = 7×6 = 42
the square with number 8 will face the square with number 9 = 8×9 = 72
The smallest product is 42