This is the "before" window prior to shiplap and window framing and trim.
The first step is to remove the wood piece along the window sill.
There is some half round trip underneath that must come off first. I pried it off gently and easily with my pry bar.
To get the lower wood piece free I gently tap with my hammer in an upward fashion. This successfully breaks the friction enough to be able to slide my pry bar underneath.
Shown here is the pry bar to pry up on the window sill piece. I was able to successfully remove it using this method.
Once loose the board comes up easily by hand.
Some window sill pieces come out in splintery chunks. I got lucky this all came out in one easy piece.
Now it's time to get measurements form framing it all in. This was about 3.5". I go and cut the lower board first.
The lower board goes in nicely and I double check measurements for top board and go cut it.
Now I install the top board.
This is the measurement for the side boards.
I cut them with the chopsaw.
I want the trim to overlap the window space by about 1/8" so I cut the bottom board to fit by as much.
This shows what it looks like before I install the trim.
I install the trim using finish nails after I install the shiplap.
Marking and cutting.
Installing the outer side trim boards.
To make the nail divets a little more hidden we apply wood filler before painting.
I let the wood filler dry overnight.
Once dry we paint all the trim.
Here it is. We ended up doing this same things to the other windows and doors as well.