The Simple Stitch is often referred to as the "afghan stitch." You will need a long afghan/Tunisian crochet hook, preferably a size or two larger than you would use for regular crochet for the given weight of yarn. For the example photos, I used a K/6.50mm hook and a worsted/medium weight yarn. Below is a photo of an afghan hook.
In Tunisian crochet, there are "Forward" directions and "Return" directions for each row. Instead of turning your work as in regular crochet, you will always have the front of the work facing you, and the stitches are worked back and forth.
The photo below shows the first row "Forward" complete.
Next, instead of turning, you will work back along the loops.
Continue inserting your hook behind each vertical bar all the way across (photo 3).
Then, work the "Return" the same way as before: yo and pull through one loop, *yo and pull through two loops. Repeat from * across until only one loop remains on hook.
Keep repeating this pattern and you will get a design that looks like the photo below!
For additional and more in-depth photo tutorials on other Tunisian stitches, plus some fun projects, see my ebook "Learn Tunisian Crochet" available HERE on Amazon!