TheMacJedi

First I measured the window (34″) and then I went and found an animal cushion close to that size and would fit properly.
It was a simple matter of using high grade 3/4″ plywood, wood molding, molding corners, wood glue, a few nails and some white spray paint.
After it was finished I screwed it into the window sill with 3″ wood screws and added the two support brackets.

Pictured below is my cat Brisco and he is a large tomcat.

I have three large cats and two of them fit comfortably in the bed.

The corner post make nice face scratchers.