I work up the concepts in Photoshop first, so here is the concept. The scene is from a photo, and the canvas is about 4 feet wide.

The outer edge will be primed canvas, with no painting on it other than the gesso. Since this canvas is a two-inch thick no-frame stretcher, the effect will be that the unpainted edge surface "frames' the image. I have done others like this in the past that had unprimed canvas in areas. It is a stunning effect.