Details needed for Pompeii oven instruction w angle iron frame

[marinwood]

Page P 41 of the 'Pompeii oven instructions", recommends using an iron angle framed opening. Unfortunately picture 8.1 does NOT show how to create a 'reveal for the door jam'.

Does anyone has a picture how this can be accomplished using 2 iron angles (2 feet each). I can not figure out how to create the upper door jam.

Thanks.