So I've been working on the same part for a couple of days and it's time to reach out to the community. I'm reverse engineering a telephone, and I'm stuck at the point where the handset fits into the base.

My approach was to build the handset, and then use it to make a subtraction from the base solid, which resulted in two cutaways for the earpiece and mouthpiece. The trouble I'm having, is creating the surface between the cutaways for the earpiece and mouthpiece. I am having difficulty getting it to transition into the cutaways, and keep a nice fillet along the edge. I've attached some photos for reference, shout out any solutions you might have.