The PHB definition for Fey Presence has the term 10-foot cube originating from you, but since a character occupies a 5 foot square, it is hard to say which squares on the grid are affected. Usually self-origin spell and features use radius, cone, or shapes that have a center, like a 15 foot square would...
Your patron bestows upon you the ability to project the beguiling and fearsome presence of the fey. As an action, you can cause each creature in a 10-foot cube originating from you to make a Wisdom saving throw against your warlock spell save DC. The creatures that fail their saving throws are all charmed or frightened by you (your choice) until the end of your next turn. Once you use this feature, you can't use it again until you finish a short or long rest.
Anyone know how this should be played?