The thing about yard sales, warehouse sales, and the like is they often involve an assortment of items that makes coming up with a cohesive promotion strategy extra-challenging. But it doesn’t mean you can’t make an advertisement that will get people excited over the event—you can go abstract and simple with your flyers, for example.
Take a look at this modern Canva design, for instance. It makes use of a yellow background and simple shapes to get attention. Choose different shapes, colors, and text to market additional promos and discounts you might be offering.