The idea behind a memory jar is to gather little things that remind you of a person or an event. There are so many ways to put together a memory jar but they fall into two basic categories or a combination of both. You can put stuff inside the jar or you can decorate the outside of the jar. Most jars are both with decorative elements on the outside put on in such a way that you can still see what is on the inside. But there are memory jars that cover the entire jar with trinkets and odds and ends. A memory jar could also just have slips of paper with short memories written on them.
I like the idea of mostly putting things in a sturdy wide-mouth jar with minimal decoration on the outside. I think a memory jar would be a great way to share some of the little odds and ends that we collect over a lifetime but no one knows what to do with after we are gone. You could also put together a memory jar for a more distant ancestor with items that are symbolic of the person if you don’t have anything that was actually theirs.