I had a lovely instagram/twitter friend ask me how to do this when she saw my photos of the doll skirts I have been making so this is my way of doing it though I am sure there might be others out there. This is a really simple instructional post rather than a tutorial it is aimed at those who can already crochet.
To start off you need a piece of felt, or the garment you want to embellish, a large darning needle and a small crochet hook. The one I use is 2mm and I am crocheting with 6 strands of embroidery floss, as you can see this is very small scale.
To start poke a hole into the felt with the darning needle, not too close the the edge or it could pull through and tear. Gently wriggle the needle around a little to create a hole your crochet hook will pass through. This will be the starting point. I usually make a knot in the yarn/thread and then pull a loop through from the back, bringing the knot up against the felt. this creates the first loop to form a stitch with.
Make a second hole with the darning needle as you did for the first. Using the loop you created do a single crochet and use the hole you have just created as the anchor point for your second stitch, continue in this fashion making holes an equal distance apart and similar depth from the edge of the felt, until you have finished.
I hope I have explained this clearly enough to be understood, I have largely taught myself to crochet so do not know all the correct terminology feel free to ask any questions and I will do my best to answer them in the comments.
I'd love to see what you make if you give this a try :)
Its a bit time consuming but gives a really lovely result.