Rear main seal question

Hi Joe, just a quick question regarding the rear main seal install. And this is for the MK1 not sure how it is done for other years, so I am currently in the process of getting my engine of the stand where it has been sitting for almost a year so i am super excited. i shall get it up on the hoist in order for me to install the tranny and a new rear main seal. I shall probably make a vid for you guys. Considering this is my first build and first time installing a new rear main seal, there is no information in the shop manual explaining how to properly install the seal into the seal casing or housing that is aluminium, that bolts onto the block with 3 10mm nuts. Some say that the seal should not go into the seal housing and bottom out meaning completely flush towards the back but leaving a little space inwards and not flushed from the front outer edge. i hope I have managed to explain what I mean but i am now going to make a video. Last thing I need is doing it incorrectly and having that dreaded oil leak.
Thanks Joe and hope this message finds you in the best of health.