There is no angle needed on a stool, just the outside sill has an angle.
Your stuck now with having to replace all the trim because you cut off those two side pieces, no way would I try and just patch in a piece!
There is no need for a router.
Apron goes on first, stool then the two side pieces.
The stool gets notched out using a jig saw so it will fit tight against the window frame.
The fastest way to mark the needed cut is with a compound mitre square.
https://www.homedepot.com/p/Kapro-1...CH=REC-_-plpsearch_multi-_-NA-_-203640795-_-N
Your stuck now with having to replace all the trim because you cut off those two side pieces, no way would I try and just patch in a piece!
There is no need for a router.
Apron goes on first, stool then the two side pieces.
The stool gets notched out using a jig saw so it will fit tight against the window frame.
The fastest way to mark the needed cut is with a compound mitre square.
https://www.homedepot.com/p/Kapro-1...CH=REC-_-plpsearch_multi-_-NA-_-203640795-_-N