First I measured the window, and we added 2 inches. We cut a piece of foam to go across the front of the window, and one inch pieces to box it in. Like in this picture:
Once the pieces were put together we ended up with this:
I then laid these on the fabric and cut it to fit and pinned it to cover the foam. I forgot to take pictures of this step, sorry! Once the fabric was pinned I ended up with this:
It was super easy, took no time at all, and we like how they turned out!