The trick with preparing carrots for your wok recipes with jumbo prawns is to get the pieces of carrot about evenly sized in spite of the fact that a typical carrot is narrow at the bottom and thick at the top. The solution is called 'roll cutting' where you hold the knife at a close angle to the long axis of the carrot and after each cut roll the carrot about 1/4 to 1/3 of a turn.
Some Roll Cut Carrots
It's amazing how all the pieces end up about the same, not matter now thick the carrot. Practice with slightly different variations and you can make longer cuts or shorter stumpier ones to make more cubic pieces. We roll cut our carrots in a size which allows us to place them in the wok as one of the first ingredients for the meal (we usually use the one-pot wok method for wok cooking as it is most convenient).