It has transpired that since the dawn of time we have all been pouring juice cartons in the wrong way risking splashing the cartons contents all over the place! The correct way to pour it is either form the side or the top (not the bottom as most of us tend to do) and that way you'll get fewer splashes!
After recovering from being MIND BLOWN James tried using the correct method to pour some Oat Milk (don't ask! We think he's turning in to a Vegetarian/Vegan) and somehow managed to spill some - it turns out he wasn't using the correct method correctly!
If there is a flap near the pouring spout you need to do this: