Lower-end wooden frames in the U.S. run about $40. You can make your own frames, but it requires a mitre saw or box saw/mitre box. Cut your trim lengths with the interior dimensions being slightly smaller than the picture (say, 17.5" by 23.5"). Glue, clamp, staple. Then, once dry, on the reverse side create a cradle slightly larger (18.25" by 24.24") than the canvas, using square dowel or trim. Glue and tack. Finish the frame using stain, tung oil, etc. Then use mounting hardware, usually sold at hobby stores, to secure the canvas frame and install a hanger wire. This, to me, is not worth the trouble, but your mileage may differ.