The sticker magic
Up until 2021, we put a blue dot on the corner of the glass. The side of the blue dot is the side that faces the talent (the human presenting).
After 2021, we added two little stickers, on each side of the glass. One sticker has a smily face, the other a camera icon. So it is easy for you to figure out which side is which.
Lost the sticker?
A simple reflection test on the glass will indicate which side faces the camera and which side faces the presenter. Put your fingernail against the bottom of the beamsplitter glass. If there is a gap between your nail and the reflection (about 3mm) of your nail, then that side faces the camera. If you turn the glass around and do the same process, then your fingernail should be right against the reflection (no gap); this side faces the presenter.
Still not sure? Watch this: