I ended up trimming everywhere, including the inside and outside of the legs. When I got to the upper portion of the mantel it got a little tricky. The width I had made the crosspiece wasn’t very wide and appeared squatty, especially when I was starting to trim it. I knew I needed to add height. I couldn’t add a ton without rebuilding the entire thing so I decided to add the top trim so it lined up with the top of the mantel. I used 1×4’s here because the top inch of these pieces will be covered by crown moulding. I had to rip out the 1x3s I used previously (but I reused those on the hearth trim) and make 1x3s that were taller. This was a good decision because it balanced out the mantel so much more.
Once those were in place I used scrap wood behind it to give it more stability. Then I wrapped the entire mantel top with a 1×2 piece of scrap MDF I had in order to give the mantel just a bit more height. I wanted the top cross piece to be the same height as the legs are wide.