Before I asked the question how small a ring can you tat, you'd probably never had reason to think about that before. Before you actually tried to make a ring as small as possible, you probably had an idea of how big the ring would be. If you are an experienced tatter you would have come closer to the right answer than a novice tatter. That's what experience does. It gives you a greater sampling of projects to work out your answers from. Even when you have the experience, sometimes actually sitting down and tatting gives you some surprises.
Some of what this course does is make you THINK. If you want to learn to design, it's not usually just a whim. Most people who want to design have a specific purpose in mind. When I began designing, I wanted some lace for the neckline of a dress. It was a plain round neck and it needed something to make a statement. At the time, pre-internet, I had few books and none of them had anything like what I wanted.
I started looking at edgings and most of them weren't wide enough for what I imagined. In retrospect, I was probably looking for a collar, but my tatting experience wasn't up to tackling a collar. I finally selected the widest pattern edging I had from the Dover publication, Tatting Doilies & Edgings edited by Rita Weiss Figure #3 which you can see here:
With the straight edge along the neck, I ended up with an edging of points which wasn't what I wanted. So I tatted a row of ring and chain around the points and a cloverleaf in between the pattern repeats which gave me a nice scalloped edge. The skinny little chain along the bottom wasn't going to leave me much to attach to the neckline, so I followed the profile with a border of cloverleaves, small ring, large ring, small ring to finish it off and added a couple of rows of crochet to give a nice straight edge for sewing it to the dress, which you can see in the picture below.
If it looks a little rumpled it's because it's old and has been through dozens of washings while still on the dress. It isn't great, but it isn't horrible either. Can you see the original edging? For perspective, the original edging was about 1.75 inches deep and the final collar is about 3 inches deep at it's widest point.
Did I consider myself a designer when I tatted this? No, no way, not even close. It did give me the experience of making something without a pattern. It let me start with something I knew would work, the original edging, then I could add on to it to get the kind of lace I wanted.
You have your own reasons for wanting to design. It might be that you have an idea you want to turn into lace. It might be that like me, you want lace that fits an idea you have in your head, but you don't see any pattern for it already made. Maybe you just want to challenge yourself to see it you can make your own original piece of lace.
One of the first questions I usually ask is, what's your problem with designing. What is it that keeps you from just sitting down and creating lace? Most of the time that question gets one of two answers. The first one is, I don't know what stitch count to use. The second one is, I don't know where to start. By the time you finish this course, both of those issues will no longer be a problem.