Here are a couple of the frames.
The flashing needed to be dried and warmed up a bit. And since the snow kept piling up, a temp piece of wood was screwed up outside, to provide a bit of a wind break.
Then some really thick grey caulking was applied. Sorry that this photo is so blurry, but it's the only one I have of the caulking.
The sill is installed over the caulking. It gets shimmed up and made level.
The black stuff in between the 2 pieces of aluminum is the thermal break, so that cold won't transfer from the outside to the inside. Once it's level, it's screwed in place and the screw holes are covered with more caulk.
And then a line of caulk is put just inside the upper lip of the sill. This is where the window frame will sit.
And here is what the frame looks like sitting on the sill. It is shimmed too and screwed into place. Before the siding is put on, expanding foam will be used to seal any spaces between the aluminum and the wood.