This technique takes practice to master. When you first try it, it's going to seem awkward; at least, that was my experience. I'd been crocheting for many years by the time I learned how to do this, and even considering my considerable experience with crochet, I had a tough time with it at first.
The awkwardness comes in, for one thing, because it's difficult to keep track of what's happening on both the front and back of the fabric at once. Don't let that discourage you; like anything else with crochet, once you get the hang of it, it's a piece of cake. It just takes practice to get there.
Here's how to work the surface crochet slip stitches as shown.
Top left photo: Find the spot where you'd like to begin outlining, and insert your crochet hook in that spot from front to back.
Top right photo: Hook your yarn and pull up a loop. When I do this, I have the front of the project facing me. So you can see what's going on, this photo is taken from an odd angle that I wouldn't actually use when crocheting. I usually do turn the work over and look at the back every so often to make sure nothing strange is happening back there.
Lower left photo: This picture shows how the work looks after you've pulled up a loop.
Lower right photo: Insert your hook into the fabric again.
Next Page: The surface crochet tutorial continues.