The easiest way to froth iced milk is to use a handheld frother. I use this frother from Zulays, but any handheld frother will do (pro tip- order batteries). It was really affordable, and I use it often. If you make lattes at home or plan to, I recommend getting one.  If you do not have a handheld frother, you can also use a mason jar to shake the oat milk until it is frothy. In fact, I suggest you shake it with the ice to give it a full “shaken iced latte” feel to it. This is the truest laziest method, and I am here for it.  If you want the feel of froth, but do not have a mason jar or a handheld frother, you may also use a blender. Simply add the oat milk to the blender, and blend for 20 seconds.