I’m showing the Edit Mode on the left so it’s easy to see where I executed extrusions and insetting.
When I extruded the faces on the top piece and the ridge that appears just beneath it, I wound up with extraneous edges. To get rid of them, I would:
- Choose a corner to start from
- Select all of the extraneous verts closest to that corner vert and then select the corner vert last
- I’m on a PC, so I hit “Alt M” for Merge
- Then I hit “L” for To Last
This merged all of the unneeded verts to the corner where I wanted them.