here is a diagram of how I'm cutting yarn form fabric, or anything else flat. It makes a long cotinous strip which you can wind into a ball as you go, if the strip is 1cm wide and the fabric is 1m square that's 100metres of yarn. A few metres of fabric should give yu enough to knit a smallish garment.
try this out on a piece of paper, cut a slit near one edge, cutting until just before the edge. then start at this side and cut a slit across above the first one, again stop cutting just before the edge. if you keep doing this all the way along you will have a long strip of paper joined by little squarish bits. These little squares do show up when you knit with fabric cut like this, but they're not very noticeable and tend to add to the look and texture, they're a lot better than knotting or sewing lots of short strips together anyway. I hope that helps, its actually a really simple technique but it's not too easy to explain.