I always have two of each item * on the table * and at least another two * under the table * - customers at craft fairs are more likely to buy if they believe there’s a chance you’ll sell out of the items they want.
Also - put the two items on the table in different spots, not side by side. I do groupings of similar items to be seen both coming and going if that makes sense. Not only does this push the scarcity mindset button, it helps spread out table traffic.
You know… I should really do a whole post on optimal table management. I spent years doing conventions and ought to share what I learned.