No, you don't only have put a canvas painting in a frame,  you have other choices. The first choice, and most popular one is to stretch it over a strainer or stretcher frame. That means first making the frame and stretching your canvas over it tightly. That way you won't even see the frame as it'll be hidden inside the stretched canvas. The second choice is to mount or glue down your canvas art (only if it's an inexpensive or of no real value item) onto a board, just as you would a print or poster, and then put a picture frame around it. With this  choice, most Customers choose not to have glass fitted to picture frames this tends to  take away the feel and texture of oil paintings on canvas. The third choice is to combine the first ...