You need great aim and be lucky. I suggest that you take the puck to your back hand go wide of the net (between the hash marks and the goal post) and take a lot of back hand shots. ( being at this awkward angle the puck still wants to go into the net but there's nothing but post there) I didn't aim high too often because Id miss the net. But it depends on your type of blade also.
***I didn't get this the first time I played be a pro because I didn't edit that Per Brodeur character (randomly generated name)...CREATE A PLAYER to get this achievement.
EDIT--scoring top corner while hitting the post works, confirmed on second account