Before doing anything, please view this video of an expert showing how to do the half-double crochet stitch. Do not stitch yet.
For our purposes, here's how we will proceed. Once you have chained fifty beginning stitches, chain two more. Go into the second stitch to begin your half-double crochet. Remember, we are working with two strands from two different skeins or balls of yarn. So, when we put our hook into the chain stitch, we will pull up a loop of two threads. Count those two threads as one. When you yarn over, count those two threads as one, etc. Finish your row until you have 50 completed stitches. Follow the instructions in the video for turning your work and stitch 50 more. Remember to count each time you complete a row to make sure that you have done fifty stitches in all. Also, try to keep your stitches the same length and level of tension. Counting your stitches will help you keep your rows even. Do as many rows as you like to make a rectangular piece to fit on your kitchen counter.
Some of you may know enough about crochet to take off from here. If you are still confused, do not worry. I made a video showing how we are working with two strands, but, as it was my first video, it was a little rough. I will make another one and post it tomorrow or Monday so that you can visualize this stitch using two strands from two skeins or balls. If you need to wait until you see me do it, that's fine. Once you catch on, your project can be worked very quickly. Or, you can take it along to appointments and such and do it at your own speed. I will post the decorative edging directions when I have finished mine. If you are not finished when I am, you can refer back to it when you have completed yours.
Note, except for the decorative edging, the only two stitches you will need to know for this project are the basic chain stitch and the double-half-crochet. Remember, the rows are basically double half crochet (treble crochet for many people outside U.S., I think). You will chain two stitches when you get to the end of a row and are ready to turn it.