This seems to be a lovely technique - Tapestry Crochet - and fairly simple if you can do single crochets. (Though you can use other stitches). Making it 'flat' is a little trickier as you have to crochet from right to left, and then left to right - in order to stay on the 'right side'. However, if you crochet in the round - this is much easier as you are always working on the 'right side'. Click here for a video link, with a very good tutorial
The work can also be felted if made in pure wool.