Okay. I went and took some pictures. I just have a phone camera.
I'll use my last post to explain the pics as best I can.
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I've made some like these. Use a doll joint. A doll joint has 3 pcs.

You don't need the washer but the "button" part and the post part.
Hot glue the slinky to button side and

insert the post into the bungee cord,

sew the fabric around them and attach them.

I almost forgot the end result!

I hope the pics help make sense. I didn't actually have anything in progress to take step by step pictures.
Doll joints are great for so many things! I use them all the time. And don't throw away those washers! I use them all the time too for so many things!