Canvases are normally made from white cotton, but they can also be found in black and linen, which will create a particularly elegant effect (if you can see the original color of the canvas under the paint). The canvas on a good-quality 3D frame should be fastened to the back of the frame by staples, beware of cheap frames where the canvas is glued to the frame sides and cut very close to the frame, it is is very likely to peel off due to the moisture in the paint. The depth of the deep frame adds a decorative touch, even in the absence of a wooden frame. Different depths of deep frame are available (the most common is 1.2 inches): you may either bring several deep frames of the same size together to create a larger design, or, alternatively, play around with different depths of frame...