First, you'll cut your fabric scrap into a square using the top of the Ball Jar (or any kind of jar, really) as a guide. You want the ends of the fabric to have about 1 in extra on EACH SIDE. So it should be just over 2 square inches larger than the top of the jar.
Cut a little bit of cotton batting (a little bit smaller than the top of the jar) and secure that and the fabric using the outside of the jar top. Tie a ribbon around the border.
Cut out little pieces of construction paper and put them into the jar. We also put a small pen into the jar, but that's up to you.
So here's the gist of the memory jar:
My family has had these for years. My brother and cousins and I wrote on the papers as kids, and we still read them every year. It's now become its own tradition!