Extruded face want't to merge with intersecting profile.

ode_tujoy

Hi folks, I have a sketch entity I want to extrude to a plane, but a section of the extrude face wants to extend to match an intersecting profile, also part of an extrude.

In the SS below, the highlighted section is the face of the extrude and roughly where I'd like it to sit in the part, but it wants to merge with the incline which is part of the side profile.

I can't seem to isolate these sections and I'm stuck with what to do.

This is a "siding block" to mount an exterior light to the side of my house. Matches the contours of the siding while extending out to provide a flat mounding surface.

The first iteration turned out very nice, but when fitted it up to to the house, I didn't account for the fact the electrical box is about 1/8th" proud of the siding face. So Im going back in to re-extrude this feature so its recessed a bit more than the sides.

I thought about mirroring that portion of the sketch to the backside of the part then extrude/remove from there, but that sounds clunky as heck so I thought I'd come as for help.

This drawing is probably cringe-worthy to most of you but here we go.

https://cad.onshape.com/documents/e18a33e3324de3cb082ae965/w/820936787a6ebd5327d62817/e/bc9acbf40dceff6066897672?renderMode=0&uiState=653409d9bafa29274adee680

Any tips?
Thank you

ode_tujoy

Immediately after posting this question I figured it out. 
I would have edited or deleted this post but these things like to sit in pending-approval purgatory for a few days. 

At any rate, my solution although not clean was to create a plane on the opposite side, sketch a circle just a hair wider than the face of the mounting extrude I wanted to trim down, and extrude that. 

Fits like a charm