The T-shirt Yarn I've been working with is chunky and very heavy. It has worked up into a nice thick Potholder with a 10mm hook (US N/P)
I have made concise instructions, but it's basically a square with a hanging loop then you go all around the edge to tidy it up :)
There's only one stitch and I have used USA terms 'single crochet' the easiest stitch there is. In the UK we would call this stitch 'double crochet'. The only thing to mention is I worked the sc stitches into the front loops only of the stitches below... this gives the potholder some variety in texture. There is a photo to help you if you've never done that before.
Right click on the photo above to save the directions as an image or you can download pdf versions below...