If you just want to practice this stitch, then try making a chain of 12. This will allow you to create a sample swatch. For a larger item, such as a washcloth, scarf, or blanket, make chains in multiples of 3 until the chain is the length that you want the finished project to be.
To double crochet, yarn over the hook, then insert the hook into both of the top loops in the next stitch. Yarn over again and pull through 1 loop. Then, yarn over again and pull through 2 loops. Then, yarn over again and pull through the last 2 loops. [4] X Research source
Make sure to work the front post double crochet stitch behind the top of your last double crochet stitch, and not into the stitch. Working the stitch this way will push the yarn forward and help to form the waffle pattern. [8] X Research source
