DIY subpanel in detached garage

Looking to add an 80A panel in my detached garage, fed by a 200A main panel. We had conduit put in from the corner of the house to the corner of the shop when extending the concrete driveway. Unfortunately it’s only 1in sch 40. This being said my plan is to run 4 4 4 6 SER from the main panel through the attic (about 45ft) then exit the attic via a junction box and splice to THWN and enter the conduit to the shop panel (about 25ft). Between ChatGPT, YouTube, and google, I’m confident it will work. My main question is how to address the junction box and its location. We have brick siding and so I would imagine it would be easiest to drop out the fascia and into the box? I’m a visual learner and looking for any advice or examples.