Building a window from 8X8 glass block. How do I finish the wall?

I don’t think I’m asking that question correctly. Basically, I’m building a shower window from 8X8 glass block. It will be built within a frame build of 2X4s, very standard. But when I add the width of a 2X4 (it’s actually 3.75″ or so) plus the width of the durarock on the inside and 7/16’s OSB on the outside…. Well, I guess I’m just trying to figure out how to make it look ‘right’. I guess the window thickness will be slightly less than the wall thickness. How do I finish that? Aluminum flashing or something?